title: conditional sum not working on certain datatypes
body: <p>I have a conditional sum in my grouping</p>
  
  <p>=sum(iif(Fields!Letter.Value="Service",0,Fields!Mailed.Value)) </p>
  
  <p>I keep getting the #error on half the fields.  There all numbers.  In my proc im calling the fields that are erroring outare doing a calculation.  I tried putting those into a subquery and calling and it errored out.  Im not sure where to go from here.</p>
  
  <p>Any ideas on why this may be and how to fix it?</p>