Sales Order, Work Order & Cost

We are trying to use a sales order with associated work order to create the correct journal entries for repair services, but have not been able to update the cost on the sales order with the cost associated with the work order.  We would use the sales order to bill the customer as well as bill the correct business unit using a b/p markup based on the cost of completing the work order.  Is there any way to accomplish this?  Thanks.