don't want to split

[sylvain ferriol]

hello
i'm using emacs with two frames opened at the start.
one of the frame is the "main" and is used for editing files
the other is the "special" frame, i want to use it for displaying 
special buffers (shell, completion,...)
my screen is like that:
-------------------- ---------------------
|   main frame   | |  special frame  |
|                         | |                          |
|                         | |                          |
-------------------- ---------------------

How can i tell emacs to use this frame when i call a shell....
i don't want him to split the main window but it doesn't have to create 
a new frame....

thanks
Sylvain