domain mapping : Force User Admin to Subdomain

Hi Guys,

So I'm running a Network site with domain mapping. The plugin works great. I'm able to map abc.com to abc.example.com well.

However, when my users access the admin panel, they are able to access it via abc.com/wp-admin. Now, I ONLY want them to access it via abc.example.com/wp-admin for two reasons:

1. I would like to SSL secure the admin area
2. Some plugins are incompatible when the admin area is abc.com/wp-admin and only works when the admin area is accessed via abc.example.com/wp-admin

How can i do this?