Position Hierarchy for Req & PO

Hello All,

We got a new requirement where our client wants to implement below scenario in our test environment.

Employee A wants his purchase requisition (irrespective of amount, item category,charge acc,location) to be approved by Employee B

While the same employee A wants his standard purchase order(irrespective of amount, item category,charge acc,location) to be approved by Employee C.

Is there any way we achieve this in Position Hierarchy?

Thanks,

VB