Admin Dashboard link

I am running a WPMU site, Multi-domain plugin, Buddypress 1.5 and installed Pro Sites. I have also activated the WP admin bar.

When a new user signs up for an account they create their blog using a subdomain. My question is how do I create a link to their admin dashboard which is their subdomain? If I create a link with your Custom Admin Bar it always defaults to the main site dashboard. Is this normal for a user to be added to the main site. Is their a way to prevent access to the main site dashboard and just redirect them to their own dashboard. This can be confusing because the new user has no real access to manage anything on the main site.

I took a look at Edublogs.org and I want to do something similar. On the frontpage there is a link that directs the user to their subdomain dashboard and on their site the admin bar all the links are relative to their subdomain.

I am hoping someone can point me in the right direction. I am new to using Wordpress.