I have a problem with the following formula

=SUMIF(Sheet1!$F$3:$F$248,"<"&DATE(2007,1,1),Sheet 1!$M$3:$M$248)/SUMIF(Sheet1!$F$3:$F$248,"<"&DATE(2007,1,1),Sheet1 !$D$3:$D$248)

Based on the SUMIF statement I look at a date range and if it falls within a
certain time frame I take the sum of a dollar column and divide it by the
total cost of another column to get a %.

This works as is, but what I need this do is now is roughly the same thing
except I do not want the $0 values to column M to be calculated in the
overall formula. I believe the $0 value is throwing my outputted % number
off.

Does someone have a better way?
Thanks
Peter W