I have spent hours trying to do this I now have less hair and whats left is
turning grey quickly, please help

Im trying to create a formula that sum,s up until it hits a particular value
and then stops so for example:
A B C
0 9 0
0 10 0
0 2 0
1 5 26
0 5 0
1 10 15
So in the example above I need the formula to sum up column B until it finds
a numerical value of 1 in in column A so the value 26 would show in column C
and the calculation would then start again from the next row.

Good luck understanding this and hope you help

Cheers