how to capture yield for back-to-back work orders with only one supplier operation?

Summary:

Our customer has a requirement where, based on a customer order they send couple of components from some vendors to an assembly vendor who performs the assembly operation. sends the final product to our customer which then gets shipped to final customer. We are implementing this using a work order with one outside processing operation. We receive via PO and issue the components from other vendors to the work order. Now they have a requirement to capture yield on the supplier side by receiving more on OSP PO and then completing the work order quantity. Please suggest how can we