//business days query
select (DATEDIFF(dd, @StartDate, @EndDate) + 1) -- Number of days between Start and End
-
(
	(DATEDIFF(wk, @StartDate, @EndDate)*2) --Weekend Days
	+(case when DATENAME(dw, @StartDate) = 'Sunday' then 1 else 0 end) --Taking into consideration the startdate being a sunday
	+(case when DATENAME(dw, @EndDate) = 'Saturday' then 1 else 0 end) --Taking into consideration the startdate being a saturday
)	

//my query
declare @IssueType varchar(10)
declare @StartDate DateTime
declare @EndDate DateTime

set @IssueType = 'MyIssue'
set @StartDate = '1/1/2012'
set @EndDate = '3/31/2012'
select RefNo, FormReceivedThroughDoor, CallCompleteDate
	--,datediff(d, FormReceivedThroughDoor,CallCompleteDate) as DaysBetween
	from tbl_complaints
	where 
        (IssueType = @IssueType)
	and (FormReceivedThroughDoor between @StartDate and @EndDate)
	and (DATEPART(WEEKDAY, FormReceivedThroughDoor)between 2 and 6)