domain mapping on edublogs

Hello,

Could anyone tell me what kind of solution has been developped on Edublogs to allow their users to create such an easy domain mapping of their blogs ??
http://edublogs.org/2009/08/12/use-your-own-domain-for-free/

I have a subdomain wpmu : http://blog.enseignons.be, and I really need some help for doing that ...

Thankls
Benjamin