Restart cumulative sum if another cell equals a certain value

[ironricebowl]

Hi all, would really appreciate all your help.

Formula output will start at cell AB5 and is to be dragged down.

I would like to have a cumulative sum of column AA, but restart the cumulative sum when there is a "1" in column O.

So for example, the cumulative sum at cell AB31 should restart to 40 and at cell AB35 should reset to 68.

Is there way I could do this? Many thanks in advance to all masters in this forum!

 

[jasonb75]

The easiest way would be to enter this into AB5 and fill down.

=IF(O5=1,AA5,SUM(AA5,AB4))

 

[ironricebowl]

The easiest way would be to enter this into AB5 and fill down.

=IF(O5=1,AA5,SUM(AA5,AB4))

My goodness thanks a lot Jason! I was overthinking things!