CREATE USER IN MSSQL STORED PROCEDURE

Can you create a user and grant privileges using CREATE USER and GRANT in a stored procedure using variables from a web page? I have code in my stored procedure to insert into the USER and DB tables but when I try to connect from my web page I receive an access denied error. However, when I create a new user via the MYSQL Admin gui I have no problem connecting from my web page. MYSQL 5, PHP 5, APACHE 2, Windows xp. My store procedure code:
CREATE DEFINER=`root`@`localhost` PROCEDURE `usp_add_client`(IN parm_name varchar(16))
BEGIN
     DECLARE temp_password varchar(45);
     set temp_password = concat('test',right(rand(),5));
     start transaction;
     /*insert mymathhelper.clients (name,password,chg_password)
         VALUES(parm_name,
                temp_password,
                1);*/
     insert mysql.user
     (  Host,
        User,
        Password,
        Select_priv,
        Execute_priv,
        ssl_cipher,
        x509_issuer,
        x509_subject )
     values
           ('localhost',
           parm_name,
           temp_password,
           'Y',
           'Y',
           'null',
           'null',
           'null'
           );
     insert mysql.db
     (  Host,
        Db,
        User,
        Select_priv,
        Execute_priv)
     values
           ('localhost',
           'mymathhelper',
           parm_name,
           'Y',
           'Y');

     commit;
END