running total formula

[trevorc]

Hi all, I need a running total to keep track of items returned by date.



I have in Column A Date In and Column B Date Out, I want to be able to create a running total in C1 were if A1...A100 is not null and B1...B100 is null, meaning an item has come in but not gone out yet. And then to update C1 when this changes.

I thought it would be easy but am having trouble putting the if, count, null, not null together.

Any help would be appreciated in solving this or pointing me in the right direction.
regards
Trevor