You mean something like this?
[Prompt1 ]= UserResponse([Product Group];"Product Group")
[Prompt2]= UserResponse([Product Group];"Product Group")
[Total]= if(isnull([Prompt1]) and isnull([Prompt2])) then "Total" else "PnL For " + UserResponse([Product Group];"Product Group") + " - " + UserResponse([Product];"Product")
Sorry couldn't understand you requirement completely.