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I Gave ChatGPT a Messy Excel File. Here's What Happened

Leila Gharani

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Most people drop a file into ChatGPT, type "analyze this," and call it a day. I wanted to know if the answer you get back is actually correct, so I gave it a sales workbook you would not wish on anyone.

The transaction sheet is just codes. No names, no categories, nothing readable. To get real numbers, ChatGPT had to look up product info, customer location, and purchase type from three separate master sheets, then do the math itself. No formulas existed anywhere in the file. It had to build everything from scratch.

⬇️ DOWNLOAD the prompts here: https://www.xelplus.com/ai-excel-prom...

In this video:
The exact guardrail prompt I used before letting ChatGPT touch the analysis
How I made it inspect the workbook first and flag missing values, duplicate transactions, and hidden sheets
Three quick checks I ran to confirm it understood the basics before trusting it with anything harder
A store vs online sales breakdown by region, cross-checked against my own Power Pivot data model
A profit margin analysis where it had to pull cost data from a different sheet and calculate margins on its own
What happens when I ask it a question the workbook genuinely cannot answer

Chapters:
00:00 - The Problem with "Analyze This"
00:33 - Exploring the Complex Sales Workbook
02:12 - Setting Guardrail Prompts for ChatGPT
04:32 - Verifying Basic Check Numbers
06:08 - Test 1: Joining Tables for Regional Sales
07:25 - Test 2: Calculating Negative Profit Margins
08:48 - The Trick Question: Will ChatGPT Hallucinate?
09:50 - Learn Advanced Excel Data Modeling

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🎬 LINKS to related videos:
Don't use ChatGPT Until You Watch this Video: Don't Use ChatGPT Until You Watch This Video
Copilot in Excel Finally Lets You Personalize It: Change This One Copilot Setting for Better...
10 Copilot Chat Prompts I Use Every Week: 10 Copilot Chat Prompts I Use Every Week

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20 Comments

@LeilaGharani Creator 2 months ago (edited) Pinned

:_leilaLightbulb: Not everyone uses AI inside Excel. Some drag and drop. I'd done this test some time ago and GPT had failed so I was curious to see where things are now. If you'd like the prompts I used inside the video and some tips and tricks, you can grab the PDF here: https://www.xelplus.com/ai-excel-prompts/#download

@asvathg358 2 months ago (edited)

So, in conclusion, it completely depends on the prompt that we ask and the basic knowledge of how Excel works. One needs to know the overall logic of how things work, before one can confirm if ChatGPT is doing correctly/not. Wonderful insights.

@pratikjain6978 2 months ago

Claude really surpassed them all. I use it as my daily tool & it can do things I couldn't imagine

@ArchanaNShetty 2 months ago

This is a great reminder that AI analysis is only as reliable as the process behind it. The guardrail prompts and verification steps are the real takeaway—trust, but always verify. Combining AI with solid data modeling and critical thinking is what turns insights into decisions.

@jackpot7898 1 month ago

Excellent, so the key is we must know what we want and how to explain it clearly to the machine aka prompt. The more clear & precise the prompt the best results we get. The age of common man talking to machines finally arrived

@stevenstanford8618 2 months ago

To be fair Copilot is making a good fist of doing the same work. I have used it to create fact and dim tables, identify connecting fields and create basic dashboards. Results need checking and sometimes number formatting screws results. Be careful of percentage numbers stored as decimals!

@drog2000 1 month ago

Yes the issue is you need to know exactly what you want and how to prompt it. I've tried with non-excel sheets or trying to get a formula to work, but it takes time to state exactly what your your looking for. Great Video and my mind is blown as what AI can do!

@teoxengineer 2 months ago

Thank you Leila. I'm about to finish your Power Query course and I'll analyse this tutorial very carefully. So, I guess that instead of developing a GPT prompt, it is better to know how to use Excel skills and checking/comparing every solution with every aspect.
I think this tutorial is so beneficial for everyone who uses Chat GPT to analyze every Excel file, not thinking about its outputs.

@MGA19a 2 months ago

The key is ... you have to know how to ask properly. To know this you know to know your sh*t 😀 and if you know your business and you know Excel as well then you can outsource some things as Leila shows here.

@goldilocks1964 2 months ago

Another solid, well-explained video from Leila! Loved the reminder about hidden sheets. I'm curious to learn some best practice techniques for anonymizing data for LLM? Maybe a good topic for another video or a short!?!

@bernardgrandjean7953 2 months ago

i always ask that the LLM provide the formulas (no hard coding) and to leave all the source data untouched. Helps with checking and integrity imho.

@sinahosseinzadeh736 2 months ago

Welcome to new world! 😎 Thank you Leila.

@vijayarjunwadkar 2 months ago

Thank you Leila for yet another useful video! Every video teaches something I never came across/tried before and this is what I love most about your teaching! Keep those coming! 😊❤

@pvrameshbabu 2 months ago

good one. I liked the idea "What chatgpt shouldn't answer"prompt.

@chrism9037 2 months ago

Very interesting Leila. I have personally switched to Claude and really like it. Thanks!

@mani4263 2 months ago

Hi Leila, I have been watching your videos for the last 5 years now, and I have learnt a lot from your videos. Keep doing the great work. Honestly, I would like to be half as good as you are in Excel. Your videos and explanations are very helpful in mastering any Excel function. I would like to know whether we can use a lookup function with two variables, i.e. I want to look up invoice numbers and amounts. I come across datasets wherein invoice numbers are repeated as they relate to separate suppliers. Thus, I want to use lookup function for two variables so that I do not get incorrect data as VLookup & XLookup throw in same invoice numbers for different amounts. Please help.

@angelbless45 2 months ago

Thank you for the videos!

@josed6841 2 months ago

Hi, I been trying to watch your videos for a while now. I’m not an accountant and don’t work in a big firm. I find your videos very challenging to understand and relate to the basic projects I want to build. You explain things as if they should be obvious.

@michaeldroy8762 2 months ago

We can now use ChatGPT inside Excel with the ChatGPT Add-in (Excel and Powerpoint) - available for a couple of months now
I guess this is more like the co-pilot experience and you work directly in the file on your desktop, the tables and pivot tables you creater stay in the sheet

Available even on free ChatGPT account - though I guess usage limits kick in early.

the Claude experience is to open the excel workbook inside Claude, which can be downloaded later.
Also available with free account