Release Strategy and workflow in Purchase Requisition

Hello All,

My client wants to activate the release strategy and workflow at the purch req and PO levels. They allow users to create a Preq and reference that preq to the PO, or users may create a PO without referencing a Preq. Since they have the release strategy and workflow working on both levels, what they want done is, if a PO has a Preq reference, it does not need to go through another approval process on the PO level as it has already been approved on the Preq level. Therefore if a Preq is reference in a PO, the PO workflow and release strategy should not be taken into account. Can this happen as a standard config, or will this need a "user exit"?

Thanks in advance for your help!!