how to have more than one Gnome desktop on various tty's

[Tapas Mishra]

I am having a Dell Laptop and most of the time I would be in GUI.
I switched to another console via pressing Ctrl+Fn+Alt+F3
and got a black screen.
Upto here it is all correct.
I want to have here a gui running and at the same time the gui which is on
Ctrl+Fn+Alt+F7 also keep running.

For other desktops the key combinations would not include the Fn key above

So I used startx :2
startx -- :2
startx -:2
and various other possibilities.
But each time it failed.
I searched it
http://www.google.com/search?q=more+than+one+gui+startx+lucid&btnG=Search&hl=en&sa=2
but I have not got any useful results out of it.
Can any one let me know what is the hack for doing above.