title: Repport Builder - SSRS: How do you reference a value in column group
body: <p>I have a dataset that is generating several columns when using the column grouping for one of the fields. Please see image below for example:</p>
  
  <p><img src="https://i.stack.imgur.com/e4o16.jpg" alt="Example"></p>
  
  <p>I need to add a additional column and reference the value in <code>column CD</code> for each row so that I could calculate the ratio of value for <code>CD</code> to Total for that row. </p>
  
  <p>I have tried using 
  <code>=SUM(IIF(Column2="CD",Column3,0))</code> which did not work. There must be some alternate way to referring to the column group which I am not aware of.</p>