Require updating Cloud PO line level DFF automatically based on a logic as soon as PO gets created

Summary:

I am trying to populate a PO line DFF based on a sql logic as soon as PO gets created. The buyer should be able to see the DFF populated as soon as the PO gets created through process requisition task.

real time update as I can see is only possible when the PO is approved, as the business event Create Purchase Order triggers only when it is approved, any idea how we can trigger it real time when the PO is created in incomplete status, can we use process requisition task as a trigger?.

I tried scheduled program as well in which takes all incomplete POs are selected and DFF gets updated, but this makes the buyer wait for a specific time to come back, open the PO again and submit (we have lowered the frequency till 2 min as well, but it still required buyer to reopen the PO).