Sumproduct & cells containing " "?

[Ken]

Excel2003 ... I am comparing 3 criteria ... WS2 Cols D-E-F to WS1 Cols A-B-C
.... when there is a match I wish to Sum values in WS2 Col G & return value to
WS1 Col D ... I am using Sumproduct & Formula is working fine except when " "
is found in the WS2 Col G to be summed. When this happens my formula returns
the #Value error ... If I replace the " " with "0" then formula again works
fine ...

Above said ... How do I write Sumproduct so it will ignore the cells in the
Col being summed when they contain a " "?

Thanks for the guidance ... Kha