"Jonathan it might have to do with your calculation and there is a better, more optimal way maybe to do it"
Create a combined field from [Primary Procedure Code] and [MSDRG_Code].
Then create a group on your combined field.
Tableau will create a temporary table which will be much faster than your calculation.
Dan, thank you so much. It worked like a charm. Elegant and efficient. Thank you for helping this neophyte so quickly.