Still not entirely clear how you're trying to set things up here (given that I think you might be using column in place for cell at at least one point), but here's my guess on the latest clarification:
I'm guessing you have a particular cell in your spreadsheet that tells you what your current amount is. You have a column that shows the payments you've made toward it.
Option A ) If you simply want a single cell to display how much you currently owe:
1 ) Pick where you want the current total amount owed to be. For example purposes, I'm going to say it should be cell G1.
2 ) Pick another cell where you'll display the total amount you've paid to be. For this example, I'm calling it cell F1.
3 ) In cell F1, set it up to sum the entire column of where you're entering all of your payments. So, for example, if you're sticking your payments in column D, type "=sum(D1
1000)" in cell F1. Make the sum start at the first row you've entered a payment, but have it go well past where you've entered thus far (just as long as the extra cells are currently blank). This will update automatically when you enter new values in the payment column.
4 ) Subtract F1 from the cell that already shows how much you owe. So, if that value is in cell B37, you'd type in G1 "=B37-F1".
This will make the amount you've paid and the amount you still owe update automatically every time you enter in a new payment.
Option B ) If you want each row to show you how much you owe after the payment you've just entered
1 ) How much you currently owe must be somewhere. Let's say for the moment it's in cell B1.
2 ) You're going to enter you payments somewhere. Let's say you'll stick them in column C. The value in C1 will be first payment, the value in C2 will be the next payment, etc.
3) In cell B2, type "B1-B2"
4) Copy cell B1, and paste into the full column of B. You can highlight a whole ton of cells at once, and paste across lots of them.
By doing this, each row of B will show you the amount owed before the payment you entered in that row of C. There will be one value of B where there is not value of C. That will be the current total amount owed.
Since I'm still doing some guess work of what it is you want, feel free to send me a direct message. If you can be clearer, and possibly send me an example spreadsheet so you can be more specific of what you're looking for, it'll make my responses more useful.