How to Amend the Purchase Order price after entering the Shipments as In-Transit or after Receiving

We create the Purchase Order with the Provisional Price ,PO for quantity 10 T * 100 USD ( Provisional Price)  and we enter the Shipments in P43250 as In -Transit .

For every Order , There are average 20 containers ( 20 In-Transit Line Items)  . Suppliers send the Shipment details with provisional and we enter the shipments in the system as in -Transit.

and After the End of the Month  we know the Actual price. we receive the Item before the actual Invoice price.

And the Actual PO price we finalize after the End of the Month. We buy the metals and LME Price we will come to know only after the End of the Month. So Supplier send Another Invoice with Actual price.