Hi Ramesh,
You need to maintain cost in KP26 for cost center and activity type.
You can have different cost center for each person, this can also be related in PA30 for the user personal number. (Check with your HR Consultant).
Else you need to have different activity under one cost centre (work centre), then the cost will be calculated.
User names can be input under requirement assignment tab in the operation.
Please make sure, the actual cost will be calculated once you do IW41 confirmation / CAT2 Posting, untill then this will be a planned cost.
Regards
Terence