Hi Ted,
Thank you for your quick response.
Here is the problem I have, column "Open Work Order" is a running total reset at user group level, FTE is each user's working hours, FTE Adjusted = Open Work Order/FTE. When I tried to do a running total for FTE Adjusted, it is not in the list of available fields. Then I tried add a formula fields Sum({@FTE Adjusted}, {@Group}), and I got the field cannot be summarized error. It looks like I cannot sum FTE Adjusted column 
Gwen