lead/lag sql2008

WITH T1 AS
(
    SELECT ROW_NUMBER() OVER(ORDER BY s.BBAN_ID) N, *
    FROM tblBBAN s
    WHERE --bbannummer >= '742671356' and bbannummer <= '743894723' and
    len(bbannummer) = 9
)
SELECT * FROM (
SELECT top 100
       [BBAN_ID]
      ,[BBANNummer]
      ,[BBANIBAN]
      ,CASE WHEN N%2=1 THEN MAX(CASE WHEN N%2=0 THEN BBANBIC END) OVER (Partition BY N/2) ELSE MAX(CASE WHEN N%2=1 THEN BBANBIC END) OVER (Partition BY (N+1)/2) END LagVal
      ,BBANBIC
      ,CASE WHEN N%2=1 THEN MAX(CASE WHEN N%2=0 THEN BBANBIC END) OVER (Partition BY (N+1)/2) ELSE MAX(CASE WHEN N%2=1 THEN BBANBIC END) OVER (Partition BY N/2) END LeadVal
      ,[BBANChecked]
      ,[BBANDateChecked]
FROM T1
ORDER BY BBANNummer
) AS q
WHERE q.leadval != ''
  AND q.lagval != ''
  AND bbanbic != ''
  AND bbanbic != q.leadval
  AND bbanbic != q.lagval