Summing non zero numbers in a column.

Hi, I can do basic excel formulas but this is stumping me. The formula I currently use is =SUM((C1*2)+(C2*3)+(C3*4)).

0 The column to be summed now has zeros in it and I only want the
0 sum of the first 3 non zero numbers. I believe I will need an array
.1 formula, but do not want a vba loop. Thanks.
0
-2
0
0
7