Sample data

```
     A            B
1  Date        Amount
2  Apr 1        $6,000
3  May 1        $4,250
4  June 1       $2,750
5  July 1       $1,000
6  Aug 1       -$0.075   <- This Cell/Row
7  Sept 1     -$0.2500

```

In a column of numbers (in reality 100-200 rows), when the value changes to negative, e.g. if these we're amounts owed on a loan, when the loan would be paid off by. Note the real difference between the numbers fluctuates based on interest, taxes, one-off payments etc. So I can't just count (total / payment) = number of months.

Is there a way to use Excel's formulas to determine this? This may be a case of requiring VBA (which is fine) but if I can avoid it, I'd like to.