This guide uses the official ChatGPT add-in inside Excel. The task is a scoped workbook review: understand one formula chain, propose a correction, and test it with values you can calculate yourself.
Open the official Excel add-in
OpenAI's setup instructions use Home > Add-ins in Excel. Search for ChatGPT, add it, open it from the ribbon, and sign in with your supported ChatGPT account. An organization may need an administrator to enable or deploy the add-in. ChatGPT for Excel setup
Use the official listing linked from that help page when choosing the add-in. Check that the workbook you are about to use is permitted under your workplace's AI rules.
ChatGPT for Excel works in a spreadsheet sidebar and can help build, explain, and update workbooks. Its chats are separate from main ChatGPT history and do not have access to ChatGPT Memory. Supply the workbook-specific instructions it needs. What the Excel experience does
Start with a read-first request
Name the tab, cell, expected behavior, and symptom. “The total is wrong” gives less direction than “the total in Summary!B8 excludes the new row in Orders.”
Review [SHEET!CELL] in this duplicate workbook. Do not edit yet.
Expected behavior: [DESCRIBE].
Observed problem: [DESCRIBE AND GIVE A SMALL EXAMPLE].
Explain the formula and the input cells/ranges it depends on.
Identify any fixed ranges, excluded rows, blank/text values, or error
handling relevant to the symptom. Distinguish confirmed findings
from hypotheses.
Propose the smallest correction. List the exact cells and formulas
you would change, what must remain unchanged, and two checks I can
perform before accepting it. Ask if the intended rule is ambiguous.
Read the actual referenced cells. An answer may correctly describe a formula while misunderstanding your business rule. A canceled order might deliberately be excluded; a blank quantity might mean “not confirmed,” not zero.
Test with a case you can calculate
Here is a fictional arithmetic fixture, not a result from running the add-in:
| Item | Quantity | Unit amount | Expected line amount |
|---|---|---|---|
| A | 2 | 15 | 30 |
| B | 3 | 8 | 24 |
| C | 1 | 12 | 12 |
The three line amounts sum to 66. If a total formula includes only the first two lines, it returns 54. The 12 difference identifies the omitted line in this small fixture; it does not prove the same fault exists in your workbook.
Check how the proposed fix behaves when a row is added. A correction that merely extends a fixed range by one row might repeat the problem next month. Ask why the suggested reference style suits the workbook's actual structure.
Also test an empty input and any status that changes inclusion. Write the expected result before accepting the new formula, so you do not end up approving whatever number appears.
Approve a narrow change and inspect the result
Apply only the correction we agreed to in [EXACT RANGE]. Preserve
the source data, other formulas, sheet names, and formatting.
Afterward list each changed cell with its old and new formula,
then report the result of [SPECIFIED TEST CASES]. Stop and ask before
changing any additional range.
A prompt is not an access boundary. Compare the changed cells and totals yourself. OpenAI recommends reviewing formulas, calculations, citations, and changed cells, and duplicating important files first. Advanced features such as VBA and macros may not be fully supported. Current limitations
If the result differs from the expected test, keep the duplicate and investigate before replacing the working copy. If you cannot get the add-in enabled, ask your administrator about the official setup rather than installing a similarly named tool to work around the restriction.
Leave an explanation the next person can use
Record the corrected cell, the rule it now implements, the test values, and who reviewed it. Keep that explanation with the workbook. A checked formula is easier to maintain when the next person can see why it was changed.
Optional: read a review note in NOS
If you prepare an HTML note explaining the correction, you can read it in NOS before sharing the explanation. The workbook remains the calculation source; the note does not synchronize cells or replace the tested Excel file.