We see this problem all the time, and it's not because you don't understand spreadsheets. It's because the tools you're using expect you to think like a programmer, not like a person managing a budget. The user who posted this scenario knows exactly what they want: a cell that starts with their new additional budget and decreases to zero as they allocate funds to the original budget line. That's a clear, human goal. The frustration comes from trying to translate it into a formula without the right mental model, or the right tool.
The formula itself is straightforward once you reframe the problem. You want cell L10 to act as a running balance. As you add amounts to N7 (the original budget), the tracking cell should subtract those additions from L10. So if L10 holds the new budget of, say, $5,000, and you add $1,000 to N7, the tracking cell should show $4,000. The simplest way is to put `=L10 - N7` in your tracking cell. But that only works if N7 is the *total* of all additions, not just the starting value. If N7 is static and you're adding increments elsewhere, you need a sum of those increments. That's where the confusion sets in, because explaining "I want to subtract the sum of all values I enter in this column from this fixed number" is harder than it should be.
What this reveals is a deeper friction. Traditional spreadsheets force you to predefine every relationship, every reference, every edge case. You have to know the exact syntax for subtraction, absolute references, and conditional logic before you can solve a simple allocation problem. AI can help, but only if you can articulate the logic in a way the machine understands, which is exactly the barrier you're hitting. The real innovation isn't a better formula cheat sheet. It's a spreadsheet that understands your intent: "track how much of this new budget I've used as I fill in my original budget line." That's a natural-language problem, not a formula problem.
You shouldn't have to remember a function or guess the right keywords for a search engine. The solution is a tool that interprets your plain-language goal and generates the logic for you. Until then, the formula `=L10 - SUM(N7:N100)` (assuming you'll add budget values in N7 and below) will work. But the takeaway is bigger: the future of data management is about removing the translation layer between what you want and what the spreadsheet executes. You're not asking for something complicated. You're asking for clarity. And that should be the default, not the exception.