Virtual Hosting again..

Hi, I am currently hosting some friends' web sites. I would like to have it look like http://username.mydomain.com instead of http://www.mydomain.com/~username through the use of public_html directory. By using username.mydomain.com, currently I have to add a virtual host tag like this:

<VirtualHost 1.2.3.4>
ServerName user1.mydomain.com
SeverAlias www.user1.mydomain.com
DocumentRoot /home/user1
</VirtualHost>

Then in the named zone file, I have to add an entry that would look like this:

user1 CNAME mydomain.com.

Or else it won't work when user1 try to access http://user1.mydomain.net.

and restart the named and apache server. This is ok, but a little bit of work. So my question is that if there are any way at all to do this dynamically through apache only but not through named.