Fixing existing workbooks with Copilot in Excel: Plan, Edit, Chat, and reviewing change scopes

About this articleThis article was created using an automated workflow leveraging generative AI. It was generated by ChatGPT and verified through a five-role self-QA process (Structure, Beginner UX, Official Sources & Technical Facts, Privacy & Safety, Editorial Quality & Redundancy) within the same execution run. This article has not been independently reviewed by another AI or verified through hands-on operation with actual Excel/Copilot software.

Verification status: 📘 Official Microsoft information confirmed / Unverified in actual environment Information verification date: October 29, 2026

When asking Copilot to modify an existing Excel workbook, asking it to "Edit" right from the start is fast, but it makes it difficult to track which cells or formulas were changed. In practice,reviewing proposed changes with Plan, applying them with Edit, and having Chat explain the resultsmakes it easier to balance execution speed with reviewability.

This article does not cover analyzing files attached to Copilot Chat or creating a new workbook from scratch using Excel Agent. It applies toworkflows that directly edit an existing workbook using Copilot within the Excel app.

Try first: 3 things to check before making changes

1. Instead of using live data, prepare a copy of a test workbook populated with the 8 sample rows shown below.

2. In Copilot within Excel, use Plan to check proposed changes and the target sheet, and proceed to Edit only if approved.

3. Chat can then explain the results of the changes, allowing a human to manually verify the actual cells, formulas, and department totals.

What to check after the operation: The expected value calculated from aggregating confirmed rows only is a grand total of 258,000 yen(East Japan: 54,000 yen, West Japan: 144,000 yen, Chubu: 60,000 yen). This result is calculated from mock data, not actual measurements from running Copilot. If you do not have access to the application UI, you can follow the table and prompts below on paper.

Prerequisite Products, Accounts, and Entry Points

According to current Microsoft documentation, Copilot in Excel has three modes: Edit, Plan, and Chat. Edit directly modifies the workbook, Plan presents a structured plan before execution, and Chat answers questions and performs analysis without altering the workbook. Additionally, current Excel tips note that it works whether AutoSave is on or off. It is important not to apply outdated general guidance or requirements from other features directly to the current Copilot in Excel.

All three modes are available on Windows, Mac, and Web. On the other hand, iPad supports Chat and Plan with Edit rolling out gradually, while iPhone/Android primarily focus on Chat, with Edit rolling out gradually on iPhone. To avoid UI differences, the procedures in this article assume you are using Windows, Mac, or Web.

Safely testing with a fictional sales table

Instead of a production workbook, enter the following fictional data into売上明細cells A1:F9 of the worksheet. Do not use personal information or actual customer names.

Blank and canceled rows are intentionally included to verify aggregation conditions that might not be obvious in a clean demonstration. The expected result this time is to "target confirmed rows only, and exclude rows with blank quantities from the aggregation as requiring verification."

Record the following before starting work:

• Whether the file売上集計-copilot-test.xlsxwas copied as

• Sheet names and sheet count

• Row and column counts of the source data

• Presence of formulas in columns up to F

• Whether Excel's calculation mode is set to "Automatic"

• AutoSave status and whether OneDrive/SharePoint version history is available

This record serves as a baseline for evaluating diffs before and after changes, rather than assessing whether Copilot's response merely looks correct.

1. Verify only "what to change" in Plan mode

First, select Plan mode and paste the following prompt.

このブックは架空の売上明細です。まだブックを編集せず、実行計画だけを作ってください。

目的:

1. 売上明細をExcelテーブルにする。

2. G列に「売上金額」を追加し、数量×単価の式を各データ行へ設定する。

3. 状態が「確定」で、数量が空欄ではない行だけを集計対象にする。

4. 新しい「部門別集計」シートに、部門別の売上金額を示すピボットテーブルを作る。

5. 同じシートに部門別売上の縦棒グラフを作る。

計画には、変更するシート、追加する列と数式、除外条件、作成するピボットテーブルとグラフ、既存セルを上書きする可能性を明記してください。
不明点がある場合は、編集せずに質問してください。

The expected observation here is not a simple response saying "It can be done." Check whether at least the following points appear in the plan.

• The target of changes売上明細and the new部門別集計are limited to

• The sales amount formula is "Quantity × Unit Price"

• 取消The handling of rows and blank quantity rows is explicitly specified

• The plan is designed not to overwrite existing columns or other sheets

• The data sources for the pivot table and chart share the same aggregation criteria

If exclusion conditions are missing or ambiguous, such as "handle appropriately", do not execute it as is. The value of Plan lies not only in having the AI think, butalso in breaking down the work into a granularity that humans can review.

2. Apply in Edit and observe the scope of changes

If the plan is as intended, submit the request in Edit mode as follows:

承認した計画を実行してください。
編集対象は「売上明細」シートと、新しく作る「部門別集計」シートだけに限定してください。
実行後に、変更したシート名、追加した範囲、設定した数式、除外した行の理由を一覧で報告してください。

Verify that the stop button is available while running, and stop the process if changes spread to unintended sheets. After completion, do not rely solely on Copilot's self-report, but verify the following in Excel:

1. 売上明細Whether it is converted into a table and the original 8 data rows remain

2. 売上金額Whether each formula in the column references the quantity and unit price in the same row

3. Whether rows with blank quantities are not silently treated as confirmed at 0 yen

4. 取消Whether the 36,000 yen from the row is included in the aggregation

5. 部門別集計Whether sheets other than the target have been added, deleted, or renamed

6. Whether the totals of the pivot table and chart match

Under these conditions, the total sales for confirmed items with quantities is 258,000 yen. By region, East Japan is 54,000 yen, West Japan is 144,000 yen, and Central Japan is 60,000 yen. East Japan Gamma (blank quantity) and Central Japan Beta (canceled) are excluded from the aggregation. These are expected values calculated manually from the sample data provided, not measured results obtained from executing in Copilot or Excel.

When numbers do not match, do not fix the AI's explanation first; instead, verify the formulas, filter conditions, and pivot table data ranges. Even if the chart alone is correct, if the source pivot table is incorrect, it fails.

3. Have Chat Explain "Without Making Changes"

Use Chat mode to review edit results.

ブックを変更しないでください。
現在の「部門別集計」について、次を説明してください。

- 集計対象になった行と除外された行の条件

- 部門別売上の合計

- 売上金額列で使われている数式の考え方

- ピボットテーブルとグラフの参照関係

- レビュー担当者が確認すべきセル範囲

Chat is meant for obtaining explanations and insights without making modifications. However, the explanations returned here must also be verified. If they do not match the actual formulas or filters, do not accept them even if the text is fluent.

Rerun by Changing Only One Condition

Once the initial test passes, change only the aggregation axis from "Department" to "Product." Do not change the formulas, target rows, or exclusion conditions.

既存の売上金額列と除外条件は変更しません。
「部門別集計」シートを複製して「商品別集計」を作り、商品別の売上金額を示すピボットテーブルと縦棒グラフへ変更してください。
元の「部門別集計」と「売上明細」は変更しないでください。

With this single condition change, the expected totals are Alpha 168,000 yen, Beta 54,000 yen, Gamma 36,000 yen, and a grand total of 258,000 yen. These are also manually calculated values based on mock data. If the grand total remains the same as the initial run while only the breakdown changes, you can separately verify that the aggregation axis was changed and that the exclusion conditions were preserved. If you change multiple conditions at once, you will not be able to identify the root cause when discrepancies occur.

Common Pitfalls and Reasons

Copilot Button or Mode Does Not Appear

Check your subscription, signed-in account, app update status, and administrator settings. Priority access and available features may differ between tiers equivalent to Basic and Premium. Switching models requires additional licensing terms, and Anthropic models cannot be used unless the administrator permits sub-processors.

A Wider Range Changed Than Planned

Broad requests such as "Clean up the sales document" are easily interpreted as including formatting or sheet structure changes. Explicitly specify target sheets, added ranges, and ranges to preserve, and verify the boundaries in Plan first. In co-authored files, changes are visible to other users, so prioritize testing on a copy.

Total Does Not Equal 258,000 Yen

Possible causes include blanks being treated as zeros, cancellation rows not being excluded, numbers formatted as text, or the pivot table reference range not expanding to additional columns. Have a human inspect cell data types, formulas, filters, and reference ranges before re-prompting Copilot.

Formulas Are Not Updating

The Copilot in Excel FAQ states that Calculation Options must be set to "Automatic." In workbooks set to manual calculation, displayed values will not update even if formulas are present, which can be mistaken for an AI failure.

Unable to Revert the File

Testing on a production file with AutoSave enabled can make changes immediately visible to co-authors. Prepare recovery options in this order: create a test copy, disable AutoSave during experimentation, and check OneDrive/SharePoint version history. Whether to disable AutoSave should align with your organization's operational policies.

.xlsxYet It Still Doesn't Work

Files checked out in SharePoint or saved in Strict Open XML format have limitations. Do not judge by the file extension alone; verify the file format and library settings.

Criteria for Production Adoption

Do not decide whether to adopt a tool simply because "a clean table was generated once." Test it at least three times using the same dummy data and record the following:

If you write a lengthy prompt for a small edit that a human could finish in a few minutes, the benefit is limited. On the other hand, if you can run routine aggregations across multiple sheets after confirming scope boundaries in Plan, you can reduce task duration while preserving the review process.

The final adoption criteria consist ofcorrect results, a limited scope of changes, and fast rollbacks.Rather than focusing on Copilot usage frequency or response aesthetics, it is safest to expand adoption starting only with tasks that satisfy these three points.

Official & Primary Resources

• Get started with Copilot in Excel — Roles of Edit, Plan, and Chat, supported apps, and directly editable deliverables

• Frequently asked questions about Copilot in Excel — Requirements for licensing, co-authoring, calculation methods, file formats, and model selection

• Copilot in Excel tips — Current notes regarding AutoSave, version history, and model selection

• Turn on AutoSave in Microsoft 365 apps — AutoSave settings for files on OneDrive/SharePoint

Specifications and available features are updated over time. Prior to publication and actual deployment, please verify your tenant's subscription, admin settings, and Excel UI display.