point blog to other domain name?

Hello

I have set up my WPmu site on a domain, now i want to point the blog a create for new users to other domain name

like this:

mywpmuhost.com/blog1 ---> myblog.com
mywpmuhost.com/blog2 ---> myblog2.com
mywpmuhost.com/blog3 ---> myblog2.com

How can i do this?