How to tie a sales order to a PO that has already been created?

Hello All,

We created a Purchase Order prior to getting a customer PO. We just got the PO from the customer today and entered a drop ship Order Confirmation. Is there any way to tie this PO to this drop ship sales order or do we need to cancel the PO and create a new one? Problem is this is shipping Friday from the vendor and we already received the product to the PO.

Normally we have some time to cancel the PO and enter a new one. Plus this has already been received. Please let me know if this can be done.

Thanks