title: How to add a total count column for an expression field
body: <p>If I have a table (tablix) in SSRS, and one of the columns is a simple expression:</p>
  
  <p><code>=Fields!NumPorts.Value - Fields!PortsUsedLastQuarter.Value</code></p>
  
  <p>Then how can I add a "total count" column for this? I can't add a total column, it's greyed out because it's an expression and not a simple field.</p>
  
  <p>Thanks</p>