title: Excel pivot table calculated field total returns unexpected value
body: <p>I have an Excel spreadsheet which has a pivot table on it. The data itself is quite simple, Number of Units and a Discount (percentage from 0 to 100), pivoted on date across the top and customer down the left hand side. Those numbers are straight from a SQL view, so the pivot table source is just:</p>
  
  <pre><code>SELECT * FROM UnitDiscountView
  </code></pre>
  
  <p>All was looking fine until I attempted to add a calculated field of TotalCost (Each unit will costs £200) to the pivot table:</p>
  
  <pre><code>= (200 *NrUnits ) * ((100-Discount)/100)
  </code></pre>
  
  <p>The total at the bottom was negative, and vastly more than I was expecting as a number. If I select all the cells, then the sum which appear in the status bar at the bottom is what I would expect, but the Total field at the bottom is over a hundred times bigger, and negative to boot.</p>
  
  <p>I am stumped. I have searched since Friday without finding anything which will help me to solve this. Any pointers on where to start looking for the solution would be greatly appreciated. I should mention that SQL is my forte, not Excel. I haven't used Excel's Pivot tables before last week, so I am probably missing something really obvious.</p>