I have to tally a year's worth of monthly data of attendees by one county's
zip codes into one main list of zip codes. (ie. San Francisco County has 20
zip codes, in January only 8 zipcodes were represented, February 10 were
represented, etc.) How do I tally each month's zip codes and attendee count
into the main excel sheet w/ all of SF's zipcodes if the not all zip codes
fields are used each month?