Adding additional lines to a PO

We are in E1 9.2 release 22. Our buyers need a process to add a line to an existing PO @ status 440 that will send the PO through the approval process. Currently we only require approval on the original requisition. Each time an invoice comes through that requires adding funds to the original PO the buyer creates a requisition sending it through the approval process, the approval is captured in screenshot to record the req was approved, the req is canceled. The buyer then goes to the original PO and adds a line with the approval screenshot attached.

Is there a was to associated multiple req's to a single PO after the PO has been released? Or is it possible to set up a version of the PO that requires approval and add lines to the PO itself that go back through approval each time a line is added?