May i ask why you want to achieve something like that? Since your Page inherits from base type Page it allways should have access to the Session-Property. One thing you can try is to implement a BasePage-class that inherits from Page. In this class you set the access to Session as a private Member. e.g.:
private HttpSessionState Session
{
get{return base.Session;}
}
But i dont know if this will work.
When in trouble, when in doubt, run in circles, scream and shout