title: Compute percentages in a PROC REPORT
body: <pre><code>PRODUCT CODE Quantity
  A         1   100
  A         2   150
  A         3    50
  total product A 300
  B         1   10
  B         2   15
  B         3    5
  total product B 30
  </code></pre>
  
  <p>I made a proc report and the break after product gives me the total quantity for each product. How can I compute an extra column on the right to calculate the percent quantity of product based on the subtotal?  </p>