cumulative logic is not working in bex

Hi Experts,

i have a requirment to develop a report on the below listed data.

now i have to make a selection screen on :

proj   , wbs , and Start date and End date.

and rep output will be like:

WBS     NETWORK   ACTIVITY  scope       cumulative work up to start date      *** work up to end date.

for this i have made a   characterstic restriction on proj , WBS . & Date  with interval.

but i am not able to apply the logic for cumulative up to start date and end date.

ouput is like:

so please help me to get the value for cumulative up to start date and end date.

Regard

vikas