Dynamic Sql "SET IDENTITY_INSERT [Table] ON/OFF" problem

Question

Hi Greetings,

I'm Creating an dynamic SQL which inserts data from one DB to another DB having same Schema. For tables which are having Identity Column had to turn the IDENTITY_INSERT option ON. But its seems like its not working. The statement is executing successfully but Insert statement is giving error of Identity insert.

       SELECT @Sql = 'SET IDENTITY_INSERT '+@DBName+'.[dbo].'+QUOTENAME(@tablename)+' OFF; '+
            'SET IDENTITY_INSERT '+@DBName+'.[dbo].'+QUOTENAME(@tablename)+' ON; '+
            'INSERT INTO '+@DBName+'.[dbo].'+QUOTENAME(@tablename)+' Select * from '+@SDBName+'.[dbo].'+QUOTENAME(@tablename)+'; '+
            'SET IDENTITY_INSERT '+@DBName+'.[dbo].'+QUOTENAME(@tablename)+' OFF; '
            EXEC (@Sql)

I'm using sql server 2005 Any Idea or help?

Your  response would be highly appreciated.

Thanks.