title: how to sum by two groups in crystal report
body: <p>i want to get the sum by the groups in crystal reports..  </p>
  
  <pre><code>    amount     order      id
    ----------------------------- 
      100.00       1       A001
      100.00       1       A002
      200.00       1       A001
      100.00       2       A001
      100.00       2       A002
      400.00       2       A002
  </code></pre>
  
  <p>and i want them to group like this</p>
  
  <pre><code>    amount     order      id
    ----------------------------- 
      300.00       1        A001
      100.00       2        A001
      100.00       1        A002
      500.00       2        A002
  </code></pre>
  
  <p>what i've done so far is in formula fields i make <code>SUM({amount},{id})</code> and name it byID and 2nd formula is <code>SUM({@byID},{order})</code> and name it byOrder which is it gives me an error saying "This field cannot be summarized.". uhmm..how to do this ? glad for any help :) </p>