Can i have a Running Value for a lookup set?

Hi All;

How do i have a running value for a the below expression in SSRS

(Fields!new_unitrateValue.Value) *(Sum(LookupSet(Fields!new_mainprogrammeid.Value & "," & 
Fields!new_subprogrammeid.Value & "," &  
 Fields!new_outputs.Value & "," & 
 Fields!new_claimmonthid.Value,
 Fields!new_mainprogrammeid.Value & "," & 
 Fields!new_subprogrammeid.Value & "," & 
 Fields!new_outputs.Value & "," & 
 Fields!new_claimmonthid.Value,
 Fields!new_programmeoutputid.Value, "ProgrammeOutput").length()))

Any help much appreciated

Thanks

Pradnya07