Question on shipment cost, PO creation

Hi,

I need to create an option for the PO (service entry sheet) to be created 1 PO per 1 shipment. Has any of you guys done that?

The "Generate PO" that is set on the "Shipment Cost Types and Item Categories". Options that exist in SPRO are validity 1 per day/ 1 per week/1 per month or no PO at all.

Thank you!