Generating Alpha numeric values in SQL Server like Identity property

My application has three atributes id, name, sal and a create button.
but the task is the user should not enter id according to his choice..
it should be generated automatically..... when new user is registering...
the no's should be like that a1,a2,a2.... b1,b2,..... no's should be alphanumeric...
s there any solution for this... help me out....
Answer for the above query,
 

DECLARE @ALPHA_VAL CHAR(1) , @INT_VAL VARCHAR(1000) DECLARE @VAL INT =97, @VAL1 INT =1 WHILE @VAL <= 122 BEGIN       SET @VAL1=1       WHILE @VAL1 < 1000        BEGIN                 SET @ALPHA_VAL = CHAR(@VAL)                 SET @INT_VAL = CONVERT(CHAR,@VAL1)                 SET @INT_VAL= @ALPHA_VAL + @INT_VAL                 PRINT @INT_VAL                 SET @VAL1 =@VAL1+1         END SET @VAL=@VAL+1 END

The output is

a1 a2 a3 a4 ....b1,b2,....b1000...c1,c2.......etc... to z1000

Cheers,

Venkatesan Prabu .J
Head - WWW.Kaashivinfotech.com
http://venkattechnicalblog.blogspot.com/