MacOSX Snow Leopard
Cocoa Emacs 23.2.1

I am trying to develop an Emacs Lisp program that maximizes the window.
I found and modified the following code, which was originally for Carbon
Emacs.

(when (eq window-system 'ns)
  (add-hook 'window-setup-hook
            (lambda ()
              (set-frame-parameter nil 'fullscreen 'fullboth)
              )))

(defun mac-toggle-max-window ()
  (interactive)
  (if (frame-parameter nil 'fullscreen)
      (set-frame-parameter nil 'fullscreen nil)
    (set-frame-parameter nil 'fullscreen 'fullboth)))

It does not act as I want it to.
window-system for MacOSX is "ns" I believe.

Could anyone see why it does not work?

Thanks in advance.

soichi