How to SKIP PO work flow if the approver not auctioned within limited hrs

Hi  Good Day !!!

In R12.1.3  -> we are are  using standard Purchase order approval engine.

We have  5  approver to approve PO.

One of approver   always delays to approve the PO.

So we want SKIP him if he did not approve the PO withing 3 hrs from he received the notification.

How can we implement  this option.

Kindly guide with steps.

Thanks