difference between two time fields(start time and end time)

Hi,

I am on BI 4.0 SP2 FP15

Created webi report based on BEX

Two fields are Start Time and End Time from Bex

I need to show process time (difference between start time and end time) in webi report

Start Time Format - (HH:MM:SS) - Ex 00:30:31

End Time Format - (HH:MM:SS) - Ex: 23:39:14

both times are on same day.

24 hours format

PLease help me as I tried to convert HH and MM into seconds but could not success.

Thanks for your help.

Thanks,

Raj