Hi,
It really does work. I've tested it.
Yes, you need all the $ signs.
It's better if you highlight the formula straight off this page, then copy,
then double click in cell K5, then paste, then enter, then copy down.

=IF(J5="","",$K$3-SUM($J$5:$J5))

But just one question: are the balances you have already, as shown in your
data, in Column K? If so, save the workbook, delete them, then proceed as
above.

Regards - Dave.