Which formula to use

[AndrePrevin]

Hi all

I have 3 columns of data. In the first and second columns I have a series of values and in the third column I need to use a formula which looks at the second column to see if there's any non-zero positive number there.
If there is then it must use that number and it must thereafter look at the first row and add that value to the number it took from the second row.
it must keep adding the value from the first row to the first non-zero positive number from the second row and incrementing upwards by the value in the first row.
Where it gets tricky, if it encounters a second non-zero positive number in the second row, it must then discard whatever value it has accumulated in the cell above it, and then reset the output value in column 3 to the new non-zero positive number it has encountered in the second row.
And thereafter use this new number and add it to the in-line value from the first column and keep incrementing upwards until it encounters another non-zero positive number in column 2

Sorry for the overly elaborate description
I have attached a sample below which actually explains/illustrates my problem a lot more simply

Metal produced	Sounding bar	Corrected values
0	2	2
0	0	2
1	0	3
1	0	4
2	0	6
2	4	4
3	0	7
3	0	10
4	6	6
5	0	11
1	0	12

<colgroup><col><col><col></colgroup><tbody>
</tbody>

Please kindly assist me

Thank you gratefully

 

[sandy666]

maybe

=IF(B2<>0,B2,SUM(A2,B2,C1))

 

[AndrePrevin]

Why?

 

[Sajukai]

Replace corrected values "C2" with this =IF(B2>0,B2,A2+C1) and fill down.

This checks column 2 for values > 0, if found only returns the value of column 2, otherwise adds column 1 to the previous column 3 value row above. Provides the same column 3 results as your example when filled down in column 3.