PO Approval

I have a situation and want to know if this is possible:

We use Requisition,Release and PO approval using positional heirarchy. If a position has a certain approval authority and the PO isapproved by whoever needs to approve it, now if there is a revision done and now the total amount of the PO goes over his approval limit then the PO goes to the next approver even if the revision amount is within his approval limit.

e.g.

Person A has approval limit of $10,000.00

Person B has approval limit of $100,000.00

Initial PO amount : $50,000.00

The PO will go to Person B and get approved.