Delegating PO approval notification in r12

How do you assign/delegate a notification to another user such that the user's approval limits are used rather than the approval limits of the person delegating?

1. Let's say buyer A submits a PO and it goes to his/her approver B

2. Approver B delegates the notification to another user X

3. X is able to approve the PO as after delegation X has the same limits as B

Question: Is there a way that when the notification reaches X Oracle uses X's approval limits and not B's?