title: Pivot Calculated formula: SUM(Field1)/AVG(Field2)
body: <p>I've a simple table with some amount and interval in sec by date and product name.</p>
  
  <pre><code>Month | Product | Amount | Interval in sec
  ------------------------------------------
  05-'12| Prod A  | 10     | 5
  05-'12| Prod A  | 3      | 5
  05-'12| Prod B  | 4      | 5
  05-'12| Prod C  | 13     | 5
  05-'12| Prod C  | 5      | 5
  </code></pre>
  
  <p>From this table I've derived a PivotTable with SUM(Amount), AVERAGE(Interval in sec) by Month and Product.</p>
  
  <pre><code>Month | Product | SUM of Amount | AVG of Interval in sec
  --------------------------------------------------------
  05-'12| Prod A  | 13            | 5
  05-'12| Prod B  | 4             | 5
  05-'12| Prod C  | 18            | 5
  </code></pre>
  
  <p>So far so good. Now I want to add and extra column to my PivotTable with gives me the outcome of SUM of Amount / AVG of Interval in sec.</p>
  
  <p>Adding a calculated value <code>=SUM(Amount)/AVERAGE(Interval)</code> is not giving me the right values. Excel gives me:</p>
  
  <pre><code>Month | Product | SUM of Amount | AVG of Interval in sec | Amount per sec
  -------------------------------------------------------------------------
  05-'12| Prod A  | 13            | 5                      | 1.3
  05-'12| Prod B  | 4             | 5                      | 0.8
  05-'12| Prod C  | 18            | 5                      | 1.8
  </code></pre>
  
  <p>What it actually is doing is =SUM(Amount)/SUM(Interval in sec) for every Month and Product based on the values in the first table. But I'm looking for:</p>
  
  <pre><code>Month | Product | SUM of Amount | AVG of Interval in sec | Amount per sec
  -------------------------------------------------------------------------
  05-'12| Prod A  | 13            | 5                      | 2.6
  05-'12| Prod B  | 4             | 5                      | 0.8
  05-'12| Prod C  | 18            | 5                      | 3.6
  </code></pre>
  
  <p>So literally divide pivot field 'Sum of Amount' by pivot field 'AVG of Interval in sec'.</p>
  
  <p>How to achieve this?</p>