How to Call Back or Cancel PO while it is 'In Process' status -R12.1.3

Good Morning

We are using  R12.1.3.

Purchase office generated PO and submitted for approval- using  HR position hierarchy.

One of  the approver  manager  is out of city and the PO in  'In Process' status.

We need to cancel this PO and submit with different PO hierarchy.

Is any way we can cancel this PO from front END  and current approver should get notification that PO is cancelled by ADMIN.

Thanks