Default DFF on Purchase Order Distributions based on a Lookup

Summary: We would like to default the values on two Purchase Order Distribution DFF's based on the Supplier Country, the Deliver-to Region, Requested Delivery Date and a Lookup having the data for Shipment Days

Content (required):

The requirement is to derive a date on the DFF based on Supplier Address (Country) and a look up to store the Transit Times (between Zones).

Background: We are currently managing our own Shipments from Suppliers. We tried to evaluate Buyer Managed Transport, but that did not help us as we have a split system between eBS and Cloud for Planning, Inventory and Purchasing.