I tried to create an alias or virtual host to run as different user. Well below is part of apache httpd.conf that doesn't work. Or, is it even possible?

<VirtualHost blah:80>

    user DifferentUser
    group DifferentGroup

    ServerAdmin blah
    DocumentRoot blah
    ServerName blah
    ServerAlias blah
    ScriptAlias /cgi-bin/ blah
    DirectoryIndex index.html index.htm default.htm index.shtml index.php
    ErrorLog logs/blah-error_log
    CustomLog logs/blah-access_log common
    <Directory "/blah/">
      Options Indexes FollowSymLinks MultiViews ExecCGI
      AllowOverride all
      Order Deny,Allow
      Deny from none
      Allow from all
    </Directory>
</VirtualHost>