a macro that involves an if formula

I have a combo box from the forms toolbox and I’ve listed to different inventories names that I have stored in another workbook. I receive a copy of my invoices in an excel doc, my question is how do I send that information with a macro depending onthe name that was picked on the combobox, that involves an if and I have no idea how to doit, and if possible how do i give the instruction to paste that information at the end of the inventorie. Can you help. THANKS IN ADVANCE FOR ANY INFO.