Help with CDN storage of Multisite

I decided to start using a cdn and set it up no problems with w3tc.

However, I have a specific issue and need some advice/help:

My cdn is interesting because I can STORE my media (especially videos) on their servers and this way it doesn't fill up my server.

How can I set this up with wordpress mu? Basically, is there a way I can set the uploads directory the a cname for example? Or using a rewrite on the uploads only? I have no idea and I don-t even know what to look for.

Thank you so much!