Parts Order Request

I am the middle man between dealers needing parts and the procurement team.
Currently a dealer submits an excel sheet via email, I then convert/ copy the lines (part names) on the excel sheet into subitems on under 1 main line item (the DPO#).
I would like to generate a form where the subitems filled out but the dealer are auto generated as sub items to a new main line item. an update to notify myself to review the new request, make adjustments as need and approve before sharing with the procurement team.
Apps create a new main line item, but not subitems.