title: Excel formula to determine cell ID when a series of numbers turns negative
body: <p>Sample data</p>
  
  <pre><code>     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   &lt;- This Cell/Row
  7  Sept 1     -$0.2500
  </code></pre>
  
  <p>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.</p>
  
  <p>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.</p>