I am looking for the formula which will allow me to keep a running total of
items on hand.

For example:

Quantity currently on hand is 100
I issue out 10
I receive in 5
My running total is 95

I know how to do the simple formula for this transaction, however, how do I
then, without having th add a ton of rows, add or subtract from the 95 figure
(how do I make that the old qty on hand), so if I have more issues and
subtractions...

Thanks in advance!