Cname Confusion with Domain Mapping

Hi, ok so on my hostgator account i have both domains, the main mu wp site and the site (domain) i want to redirect to my test user blog on the mu site. What i did is i created a cname on the site but it askes me to give it a name so then it saved it as blog.domainname.com and then i pointed it to my multi user site here, without the folder that the test blog site is in. I also mapped the domain i want to point to my blog in the tools>domain mapping under my test account on the mu site. Nothing happened. Then I am talking to support on the hosting account and they are telling me you can't do a cname to a subfolder... What am i to do? My goal is to be able to give my users full websites under their own domain names., WIll i be able to do that?