I am using the following forumla:

=SUMPRODUCT(--(Sheet2!$D$2:$D$396DATE(2004,6,15)),--(Sheet2!$D$2:$D$396<=DATE(2004,7,15)),Sheet2!$G$2: $G$396)+SUMPRODUCT(--(Sheet2!$K$2:$K$396DATE(2004,6,15)),--(Sheet2!$K$2:$K$396<=DATE(2004,7,15)),Sheet2!$N$2: $N$396)

The question is: How do I omit cells within the range that have #N/A
(because data hasn't been entered in that cell to make the function work)?

Thanks