Build PO as Approved

Hello, this one is for Peoplesoft 9.1 or 9.2.

We allow Buyers to select the "Build POs as Approved" when expediting requisitions since our approvals get handled on the requisition side.

However, we now have a requirement to trigger PO workflow to Legal for POs over a certain $$ amount - this is rare, so maybe 1% of POs would need this approval.

The problem is that we don't want to stop building POs as approved in sourcing (for the other 99%), but I can see a way to trigger PO WF if the PO is already created as "Approved".

Does anyone have any ideas? Trying to avoid a customization, but may have no choice if the business insists on building POs as approved.