ProjectStatus to have if the submitter is not the same put on the Approver

Summary:

We are currently developing a Project Status worklist where users will input an employee's email address to designate them as the recipient of the project closure approval notification. We have identified a potential risk: an employee might inadvertently (or intentionally) select their own name from the List of Values (LOV) and populate the designated approval notification field. This action would violate our intended separation of duties for the approval process.

To prevent this, what validation rule can we implement to trigger an error if the user submitting the project closure request is the same employee selected in the DFF field for the approval notification?