forward subdomain to subdir, transparently?

I know I can forward a subdomain to a subdirectory in my main domain. But is there a way to do this so the url doesn't change? i.e. a user goes to "easyname.mydomain.com" and is forwarded to "mydomain.com/easyname", but their browser still says "easyname.mydomain.com". I believe this can be done with .htaccess, but I've tried a few scripts and can't seem to get it right. Total noob, but willing to learn.

Set it up in the DH panel as fully-hosted instead of redirected, and use the subdirectory as the document root directory for that domain.

-- Dan

Thanks. Now it seems obvious. I wasn't even paying attention to that field in the panel.

forward subdomain to subdir, transparently?