SET @Script = 'DECLARE @S INT /* used to test for comment lines */ 
-- Another method to comment line  
SELECT * FROM logentries'

DECLARE @Pos1 INT
DECLARE @Pos2 INT
SET @Pos1 = 0
SET @Pos2 = 0
SET @Pos1 = CHARINDEX('--',@Script,1)
IF @Pos1 > 0 
   BEGIN
      SET @Pos2 = CHARINDEX(CHAR(10),@Script,@Pos1 + 1)  --CHAR(10) = line feed
   END