Service order billing in SD integration with PS

Hai Gurus,

My client is basically a civil construction one and we are in the process of

implementing SAP for them.

The scenario is my client gets sub contracting order from big construction

company and execute all the constrction and the entire related works.

The process flow is the actual service order price from the main constrction

company is around 50 crore, so my client keeps his margin and allocate

budget to execute the project as 40 crores.

Now the problem is how to integrate the SD service order billing and cost

captured for each and every activity in PS , so that my client actual cost

incurred is 40 crore but he has to raise bill after adding his profit as 50 crore

to main construction concern.

How to link this process of SD service order billing with PS.

Waiting for your positive reply.

Regards

sekar chand.