Automatically adding Req line to existing PO

We have Automatic PO Creation enabled in the workflow and therefore when a requisition line that references a source GBPA line is approved, this invokes the CREATEPO workflow to automatically create a PO from the requisition line.

However, is it possible to use this workflow to automatically add approved req lines to existing PO's? I understand there may be a customisation required in order for the Req line to be linked to an existing PO, however I am wondering if there is any seeded workflow functionality available to automatically add approved req lines to existing PO's?

Thank you