What formula should I use to count the # of days between 2 dates
excluding weekends?
=networkdays(start_date,end_date)
If you are using a version of Excel prior to 2007, and you get a #NAME error, goto HELP for the NETWORKDAYS function to see how to install the Analysis Tool Pak.
Note that this function counts BOTH the start and end dates, so depending on your requirements, you may need to subtract 1 from the result.