I'm not sure that is possible here. You would need to have wildcard DNS entries for subdomains, and mod_rewrite rules. I found some examples when I googled, but they all seemed to say that some form of DNS editing was necessary. You could fire an email off to support and ask them.
Simon Jessey | Keystone Websites
Save $97 on yearly plans with promo code [color=#CC0000][b]SCJESSEY97[/b][/color]