Tracking items in the middle of Outside Processing

Hi,

We have set up many items with two primary outside resources.  We send a P.O. to the first to fabricate any number of different parts. On that PO are also the instructions for the 2nd processing source, on how many of which items to paint what color.

When the fabrication is finished Resource A faxes us that the parts are in transit to Resource B. We receive against the Resource A PO which generates a requisition for Resource B from which we create a 2nd PO for Resource B.  When Resource B ships the painted parts back to our warehouse we receive against the Resource B PO which brings the finished parts into our inventory.