How to make Project Number mandatory on PR distributions based on Procurement Category selection

Summary:

We need the Project Number field on PR distributions to become mandatory when a user selects a specific procurement category, preventing submission without project information.

Content (please ensure you mask any confidential information):

We are implementing Oracle Fusion Cloud Procurement (Procure-to-Pay) and have a business requirement where, if a user selects a particular procurement category on a requisition line, the Project Number field on the distribution must become mandatory — the user should not be able to submit the PR/PO without entering project details.

We have explored the following approaches:

1. VB Studio — Conditional Mandatory Field via Business Rules
We investigated placing a condition on the Project Number field through VB Studio, so that it becomes mandatory when a specific procurement category is selected. This partially works — when a user navigates to the distribution and attempts to update it without a project number, the system correctly raises a validation error.