How do I set up a quantity field so that I can put a starting quantity, then
subtract a number from it, then later, come back to that same subtract field
and subtract again to get a constant quantity that is dropping to reflect the
multiple entries . Example, Qty of 100 in cell a1. In cell b1 I put 10 to
remove a1 from stock. Later I come back to b1 and type in 5. I want my
total in a1 to now be 85. Any help would be appreciated.