Can we create work confirmation with quantity purchase basis?

Summary:

Hi

Here are the procurement flow of our business process:

Requester create PR, existing system (non Oracle) is using master item in PR line, so we also create PR using item in PR Line. Then the Buyer process requisition into PO. The Buyer choose the Complex PO Purchasing Document Style, because there are PO that will be invoiced based on progress by supplier. But, item based PR line cannot be processed into Complex PO. Requester is dont know what the PR line that will be invoiced based on progress by supplier. Only the Buyer that know this information after RFQ. How to create Complex PO with PR line create