Actually, if you are willing to use a "Date Table," make it a date dimension table.  Do all of the date calculations that can be done to a date ahead of time, calculate the day of week, week of year, day of month, month name and number, etc.  You can add a column for something like "HolidayFlag" and another one for "WeekendFlag."  Now, all you have to do is go to this table with the beginning and ending dates and count the number of No's in the weekend flag and subtract the number of Yes's in the Holiday flag for the date range you want to check.

If you are interested, I can post the structure of such a table.