How to restrict user from approving the PO/RP notifications.

Hi Guru's,

How to restrict user from approving the PO/RP notifications.

Actually, two users(Approvers) are having the same position(ex: User A and B are having same position in the HRMS). Now the client says that they don't want to change the positions of the users(Approvers), but instead only User B needs approve the notifications, i.e User A should be restricted from approving the notifications.

Kindly suggest.

Thanks,
Gopi Nath