CREATE TABLE #WeekTable(
  YearCol INT
 ,WeekCol VARCHAR(9)
);

INSERT INTO #WeekTable (YearCol, WeekCol)
SELECT 2009, 'wk1' UNION ALL 
SELECT 2009, 'wk31' UNION ALL 
SELECT 2009, 'wk52' UNION ALL 
SELECT 2010, 'wk1' UNION ALL 
SELECT 2010, 'wk31' UNION ALL 
SELECT 2010, 'wk52' UNION ALL 
SELECT 2011, 'wk1' UNION ALL 
SELECT 2011, 'wk31' UNION ALL 
SELECT 2011, 'wk52' 

SELECT 
  [Week] = CASE WHEN REPLACE(WeekCol, 'wk', '') = DATEPART(wk, CURRENT_TIMESTAMP) 
                THEN '0'
                ELSE WeekCol
           END     
 ,* 
FROM #WeekTable;

DROP TABLE #WeekTable;

=DatePart(DateInterval.WeekOfYear, Today)