Use [EnVisage]

IF EXISTS (SELECT *
           FROM   sys.objects
           WHERE  object_id = OBJECT_ID(N'[dbo].[GetFCWeekEndForDate]')
                  AND type IN ( N'FN', N'IF', N'TF', N'FS', N'FT' ))
  DROP FUNCTION [dbo].[GetFCWeekEndForDate]
GO 

CREATE FUNCTION GetFCWeekEndForDate (@dt date)
RETURNS date
AS
BEGIN
	DECLARE @ret date
	DECLARE @maxDate date
	DECLARE @weekStart date
	DECLARE @weekEnd date

	if (@dt is null)
		return null

	select @maxDate = MAX(EndDate) from FiscalCalendar
		where ([Type] = 0)

	if (@dt >= @maxDate)
		set @ret = null
	else
	begin
		select top 1 @weekStart = StartDate, @weekEnd = EndDate from FiscalCalendar
			where ([Type] = 0) and (StartDate <= @dt) and (EndDate >= @dt)

		if (@weekStart is null)
			set @ret = @dt
		else
		begin
			if (@dt = @weekEnd)
				set @ret = @weekEnd
			else
				set @ret = DATEADD(day, -1, @weekStart)
		end
	end

	RETURN @ret
END
GO