if you're working in Google Blogger, then either your server is not Apache, or it is but you cannot get to it to do things like the previous suggestion.
Can you clarify why you want to do what you've descrived: what is the relationship between the new page and the rest of the blog?
Also, do you really want to point a separate subdomain to the at page (ie anyone who visits the subdomain is re-directed to the page inside your blog)? Or to have the page avaiable under its own access at the separate subdomain?
What benefits are you hoping to acheive by doing this rather than making a new blog, and using the entirely different sub-domain for it?