Ignore blank cells

I have a row of cells, say, A1 to G1.
I wish to sum the values in cells, say, A1, C1, F1 and G1 only. The chosen cells can have values 0, >0 or Blank. How do I sum the values and ignore the blank cell(s) without getting #VALUE!?
Filling the blank cells with "0" is not an option.

(Any blank cells may have a value added at a later date).

Edit: I could use multiple 'IF' statements, but this is cumbersome. There must be a simpler way.

Thanks in advance

Alan