Drop Ship PO Number via Sales Order

Can anyone help?

The problem is that we trying to stop our purchasing team from ordering items that will be drop shipped. There is a gap in time between the sales order goes on the system and the drop ship PO being created from the sales order. Therefore items show up to be ordered by purchasing that we don't need in stock.

One of our first attamepts at this was to create a search or report on items on sales orders that are to be drop shipped using a custom check box at the time the sales order is entered on the system. However, when we create a drop ship PO from a sales order the sales order reference shows nicely as the created by fields in the PO. However we are stuck trying to get the drop ship PO value from a sales order record even though it is displayed on the sales order forms. The key to the report to