How to prevent end-users from backdating the Expenditure Item Date on Req and PO lines?

Business Concern:

Users are able manipulate the Item Expenditure Date to bypass system restrictions, leading to inaccurate financial reporting and cost allocations.

The Expenditure Item Date is set to default current sys date (Project Costing DFF) for both requisitions and PO lines. However, we want to prevent users from backdating the date to bypass errors. For example, when entering a requisition, users may receive the following error:
"The Expenditure Item Date is outside the project dates. Update the project start date and finish dates or expenditure item date of the transaction."

If the user backdates the Expenditure Item Date to within the project dates, they can bypass the error and submit the transaction. We want to restrict this action.