Calculate difference between dates excluding weekends

Hi there
I would like to know how i can calculate the difference (in days) between two dates, excluding the weekends from the calculation.
For example lets say A1 has 22 May 2008 and A2 has 27 May 2008. How do i calculate the difference between A2 and A1 so i get the answer as 3. Using Networkdates gives me 4 (it includes the start date in the calculation). I can't use datedif because sometimes my first date is smaller than the second date, in which case it gives me an error.
Also, occasionally my two dates are from two different years like it can be 22 May 2007 and 27 May 2008.
It would be really helpful if someone can help with this.
Many Thanks in advance
Cheers
Nitin