SSRS 2008 Datediff for Working Days

This code is not exactly correct. A year can start or end with either a Saturday or a Sunday. For example, 2011 starts on a Saturday and ends on a Saturday. January 1st & 2nd, 2011 are Saturday and Sunday respectively and Dec 31st, 2011 is also a Saturday. The above code does not account for this scenario. The code below is correct:

= (DateDiff(DateInterval.day,Parameters!BeginDate.Value,Parameters!EndDate.Value)+1)
- (DateDiff(DateInterval.WeekOfYear,Parameters!BeginDate.Value,Parameters!EndDate.Value)*2) 
- IIF(Weekday(Parameters!BeginDate.Value,1) = 1,1,0)
- IIF(Weekday(Parameters!BeginDate.Value,1) = 7,1,0)
- IIF(Weekday(Parameters!EndDate.Value,1) = 1,1,0)
- IIF(Weekday(Parameters!EndDate.Value,1) = 7,1,0)

The SQL in the link (Number of working days between two dates) translated for SSRS: Hopefully this will give you a good place to start. Type this into the expression for the textbox.

=(DateDiff(DateInterval.day,Parameters!STARTDATE.Value,Parameters!ENDDATE.Value)+1)
-(DateDiff(DateInterval.WeekOfYear,Parameters!STARTDATE.Value,Parameters!ENDDATE.Value)*2)
-(iif(Weekday(Parameters!STARTDATE.Value) = 7,1,0)
-(iif(Weekday(Parameters!ENDDATE.Value) = 6,1,0))-1)