Customer Shipment-Cancel lines

Is there any way in Vantage 8.03 to cancel certain lines in the
Customer Shipment Entry screen? For example, I have two lines on a
sales order. Line one, I have the product for and have it ready to
ship. Line two, I don't have the product for and the customer wants to
cancel. Vantage won't let me enter a zero quantity on the Customer
Shipment Entry screen and save it. I realize that you can go back into
the sales order and delete the line, but was hoping to be able to just
close the line or something in the Customer Shipment Entry screen.