PO Approval for Change Order

Summary:

We would like to know how to create PO approval for change order.

Content (please ensure you mask any confidential information):

Scenario: We create requisition 1 with requester 1, then this requisition 1 create Purchase Order 1. There is no issue for PR approval and PO approval. Now the new situation is we create new requisition 2 with requester 2 and add into existing Purchase Order 1. There is a change order in Purchase Order 1. Now our approval is checking the requester and send for the manager. Now it check requester 1 and requester 2. Is there a way that we can only change requester 2 which is the change order.