How to recognize labor cost using Sales Order

Hello Sap Experts,

I kindly need your help. Our Company wishes to use SD module instead of CS for Services Performed. I was able to Create an sd process from sales Order directly to Billing. However the system only recognizes the Revenue portion of the Services. We wish to be able to Record Labor costs during billing if possible.

Is there a way? or if not, can there be an alternative as to how to record the labor costs using only the SD Module?