How do you do one-to-many in the BOM and OSP

We have a need to take one purchased part and send it out for OSP to make it into two different part numbers.  I need to know how to do that with a BOM and still maintain cost roll up.  Here is the example:

1. We buy part X1234 from one source.
2. We create a work order for two different jobs to drive OSP for parts Z987 and T555.
3. We send part X1234 out to the OSP source.
4. The OSP source cuts and machines the one part into two different parts, Z987 and T555.
5. The OSP source sends us the two parts and invoices us for the two different parts.