Change Password On Sql 2000?

I am trying to change password, using the code below.. The code below is in a stored proc and I am passing these parameters from a web application.....

 sp_password [ [ @old = ] 'old_password' , ]
    { [ @new =] 'new_password' }
    [ , [ @loginame = ] 'login' ]

 

sp_password 'cust1','cust2','cust1'

Server: Msg 15210, Level 16, State 1, Procedure sp_password, Line 20
Only members of the sysadmin role can use the loginame option. The password was not changed.


I made my user part of the db_securityadmin role, but that does not help...

How can I give the above mentioned permissions, so that when user cust1 logs on then he can chnage his own password from the web application as long he has given his old password correctly?