Purchase Order Entry - Field Choosing

AccountRight+ Desktop. Is there a way of changing the entry fields in the purchase order when entering inventory/item purchases please?  I want to include the suppliers code as well as our code. I’m not talking about the purchase order form that gets printed (customising the purchase order form), I’m referring to the entry screen with the desktop program. I think I recall that you can’t but all of my searching refers only to the purchase order form. 
Thanks in advance