We used to use Elements Checklist for this but they've discontinued the product. It had the ability to create item lists and you could set a price for an item. When you pulled up the dropdown list that was configured you could choose the item and a quantity. It would then show the total price of the quantity entered for that item. Somewhat like an invoice but we used it for internal tracking only. So if Bill sold 3 widget1 @ 4.00 ea and 4 widget2 @ 6.00 the line items would show:
Widget1 3 $12.00
Widget2 4 $24.00
Is there something else like that available?