Need a solution in RSSP that is similar to personalizing UOM field in PR using EL Expression

Summary:

In SSP, UOM field is personalized using EL Expression. We are looking for a solution to achieve same/similar results in RSSP

Content (please ensure you mask any confidential information):

Based on a client requirement, we have personalized UOM field in PR and PO screen using EL Expression such that :

a. If item number field is blank, then UOM field should be enabled for editing, so that requester will input required UOM

b. If item number field is not blank, then UOM field should be frozen. Item Primary UOM will default in the transaction and requester is not allowed to edit the UOM