Generating purchase orders using supplier part number/supplier stock code

We have two Item Codes that use the same part number/supplier stock code but they are actually the same item. We sell them at different prices to the same customer and wish to continue doing so and would like to continue with the two different Item Codes. However this means that the stock movement is not being recorded accurately in Sage because the stock is being picked in the warehouse from the same bay. We use generate orders in the POP module and need the facility to generate the information from the part number/supplier stock code instead of the Item Code. Can this functionality be made available please.