Advanced Billing/PO Change

We are on Pre-Pay with a Supplier and we use Advanced Billing to pay for the Invoice before the material arrives. After we paid for this material, we had to change to an alternate material due to a mill shortage. So we need to put a new PO in for the alternate material and they are only charging us the difference from what we have already paid and the price of the new material.

What is the best way to handle this? We will not be receiving the PO of the material we already paid for. For the new PO, the cost will not reflect the actual cost of the material that will be issued to the job.

My first thougth would be to create a new PO for the new alternate material, use advanced billing to get the order started for the supplier and when the mateiral is received in, make an inventory cost adjustment to the actual total cost of the material.

But i’m thinking there might be a better way. Any help is appreciated.