If you're being honest, it takes at least one to two hours to build a 13 week cash flow model, no? And this assumes that you have no interruptions, no broken formulas, and no one sending you DMs on Teams or Slack asking "quick question?" I recently built a cash flow model with two products, each with different payment terms (one at two weeks, one at three), plus leasing costs, salaries, and a machine down payment. You know, the kind of model you know how to build (but one that takes forever to execute properly). Well, I did it in under 10 minutes. And the documentation was better than most Excel files I've seen from experienced analysts. Last week, we looked at how Claude in Excel helps me do this (you can read it here) Now, I want to show you how to do this in Excel only.
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You already know how a 13-week cash flow should work. You understand receipt timing, payment terms, and cost allocation, and the logic is clear in your head.
But then you spend 90 minutes linking cells, fixing off-by-one errors in your OFFSET formulas, and formatting tabs to hide the fact you built it in a rush.
You're spending your time on linking, not thinking.
And the worst part is that the more complex the model, the more time you spend on chaining everything together instead of analysis.
You know the payment terms matter. You know the timing assumptions are critical. But you're so deep in formula syntax that you don't have time to think about whether your assumptions are realistic or not, and this will cost you some really important decision making.
Clippy – V2
Do you remember Clippy in Microsoft Office?
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It used to tap your screen, and ask whether it could help you (but it could not really do anything good)
Well, Microsoft’s Excel Agent is like Clippy – V2 (actually, more like V200), and you will be amazed at what it can do.
This is how the way we work is going to change.
You give the agent a task, and while it's working you go do something else (like giving a task to a junior team member). Then you come back, review the work, and move on. You become the architect who instructs the AI to build, and then reviews what it produces.
Excel's Agent Mode can build financial models with formulas and graphs. Plus, you can audit this with formulas you can audit, test, and change.
It explains the assumptions it made. You can click to get the details and it will walk you through the whole workbook and all of the logic.
It's even better than working with a junior in this way, because you have all of the explanations documented from the start.
How to Set This Up (And Build Your First Model)
Here's how you access it.
Step 1: Get Excel Agent Mode
First you need to open Excel. You can open it on the Web, Windows, or Mac. Next is to open Copilot and select Agent Mode from the tools menu.
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Agent Mode is now generally available across Web and Desktop for commercial Microsoft 365 Copilot licenses. However, according to the official blog, it might not be available yet to customers in the EU or UK. You can check out availability and access here Agent Mode in Excel.
Step 2: Describe Your Model Like You're Briefing a New Hire
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For my 13-week cash flow, I described two products with different payment terms (Product A receives cash two weeks after sale, Product B receives cash three weeks after). I included different prices, different units, and different cost structures. I also specified that leasing costs are paid monthly, salaries are paid monthly, and there's a machine down payment upfront.
Prompt:
The more specific you are about timing and terms, the better the output. Think of it like writing a brief for someone who's competent but doesn't know your business yet.
Step 3: Let It Build (Go Do Something Else)
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The agent will start working. For a complex model like the 13-week cash flow, expect around 5 to 10 minutes. You'll see it reasoning through the tasks in the activity panel.
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While it's working, go do something else.
I usually open another browser tab and work through other tasks like e-mail and Slack. When you come back, the model is built.
Step 4: Review Using Its Own Documentation
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When it's finished, you'll see a green indicator. Everything is explained in a panel, including how many sheets were added, the key results (like net cash per week), and how the logic works. It also explains the assumptions it made.
You can click to get the details and it will explain the whole workbook and all of the logic.
This is where your finance brain kicks in. So read the assumptions, check if the payment term logic matches your reality and check to make sure that all the links make sense
Step 5: Refine With Natural Language
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If something is wrong, you don't need to fix the formulas yourself. You can select the cells and tell the agent what to change.
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For example, I wanted to change Product B's payment receipt term to 1.5 weeks instead of 3 weeks. I just selected the relevant area and typed "Product B: change the payment receipt term to 1.5 weeks." The agent updated the formulas in about a minute.
And if there's a calculation error, you can watch it fix itself in real-time. It identifies the problem and corrects the formulas on its own.
The One Thing to Remember
The models Agent Mode builds are well designed and better documented than what a lot of people produce when they use Excel.
I've reviewed hundreds of financial models over the years, and most of them have zero explanation of assumptions, inconsistent formatting, and formula logic that only the original builder understands.
Agent Mode gives you clearer assumptions, consistent structure, and a full audit trail by default. In many cases, its documentation is better than yours would be.
So you have to ask yourself why you're still spending hours on work that AI does better and faster.
This is the beauty of having a 13-week cash flow forecast done by Agent Mode. You save so much time. Plus, you end up with better templates that you can reuse for next time.
Your value was never in the formula syntax anyway. It was always in knowing which assumptions to challenge, and you have time to do that now.
Remember this:
You're not paid to type formulas. You're paid to look out for the cash.
Best,
Your AI Finance Expert,
Nicolas
P.S. – Have you tried Agent Mode yet? Hit reply and tell me how it went (I read all replies).
P.P.S. – If you want to see exactly how I built the 13-week cash flow model, watch my full walkthrough video on YouTube here Excel Agent Mode: Build Financial Models with AI in Minutes (Full Tutorial).