Gjorde det i t-sql istället:
DECLARE @WeekNum INT,
@YearNum char(4)
SET @WeekNum = 15
SET @YearNum = 2010
SELECT DATEADD(wk, DATEDIFF(wk, 6, '1/1/' + @YearNum) + (@WeekNum), 7) AS StartOfWeek
SELECT DATEADD(wk, DATEDIFF(wk, 5, '1/1/' + @YearNum) + (@WeekNum), 6) AS EndOfWeek