Need an access query formula to decrease order quantity. Here what I am doing. I have a part number as a field and date due, quantity order and instock qty, four fields, in the 5th field I need a formula to show a decrease from the stock qty and the order qty, if I have six orders of the same part number. say I have 4pcs in stock and six orders one PC per order, I would see total at the end of mins -2pcs . can it be done? if so how?