When registering and creating an item in a document, you will find relevant CUSPARTs on a product when you search both by part number and text. Then you choose the CUSPART you want and this will be added to the corresponding field on the item. In the item table in the COA menu, you can choose
to extract a separate column that shows CUSPART. You should be able to select CUSPART when registering the item. It is possible to update on item level of an order that has status = 1.