Subdomain and mapping specific pages in SquareSpace to those pages

Greetings,

I am working on a website for a client that has a video streaming service.

We would like to have the user login be the root domain. i.e. streamtv[.]com

I also have other pages and a menu nav that I would like on a subdomain. biz[.]streamtv[.]com

Is this possible on SquareSpace? I know how to do it on other hosting platforms.

Thanks!

(ps. those domains are fictitious) 

Menu on the  nav yes, user login not exacly. You can password specific pages  that have their own url.