Could Amount PO line can't bigger from Amount PR line

Summary:

We have requirement from Customer

1. User create PR
   item : A001- Expense
   Qty : 10
   Unit Price : USD 100
2. User submit PR
3. Approver Approve PR
4. Buyer Autocreate/Process Requisition become PO
5. Buyer create PO
   item : A001- Expense
   Qty : 10
   Unit Price : USD 100 --> If buyer change Unit Price higher than USD 100 --> Could when submit PO then Automatically rejected?
   If Buyer change unit price lower than USD 100 --> PO can submit and Approved

How to setup logic for Amount PO can't higher than Amount PR?

Please share detail logic for approval

Need advice

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