PO's & BOM's

I know how to create components requirements for purchase orders but does anyone know how to create dependent PO as a BOM.

Scenario: Buy a pin (MM 999877) from vendor A on PO 123456 an have it delivered to vendor B. Create a PO (123457) for vendor B to gold plate the pin and return it to you as MM 999866. I am trying to figure out if this can be done without goods movements on the raw part but I also want costing to roll up the costs for the finished piece.

If anyone has any ideas I would greatly appreciate it.

Gordon