Requirement for change Purchase Order Approval flow

Requirement,

Whenever the User changes the PO Quantity and Price in the change Order it will follow the existing Approval hierarchy. If no amount and Qty changed it should get auto-approved.

Scenario

1. User Create PO rev-0 with PO Qty - 1 and base Price - 100. Total line amount 100
2. If the user creates PO rev-1 with PO Qty 100 and base price -1 there is no change in the Document total amount so it is going for Auto approved But the business wants it should go for the existing approval Flow.