Sum formula with conditions

Hello all,

I'm having toruble developing a formula to allow me to add all the values in cells A1 through A100 if their respective quantities are more than 0.

What i mean is if i have the following columns of data:
A B
6 2
2 1
4 0

A being the values added and B being the quantity then i only want A1 and A2 Added together. Therefore the value would be 8.

Any help to get a formula for this would be great.

Thanks

Use SUMIF

=SUMIF(B:B,">0",A:A)

You could use:
=SUMIF($B$2:$B$4,">0",$A$2:$A$4)