work order outside operations, purchase order generation and blanket orders

I've been tasked with finding a way to generate a blanket purchase order for outside services and then link the blanket releases to the work order routing requiring the outside service.  I've gotten the system to generate PO's from the operation step when the work order is created however, it's creating a regular PO and not a release from the blanket.  To date I have been unable to identify a process for making this linkage.  Has anyone successfully done this?  We're on JD Edwards Enterprise One 9.1.  Any help would be appreciated.