Toggle fullscreen with one key

[Johan Josefsson]

I am currently using two keys (f2 and C-f2) and two functions for 
maximizing and restoring the frame in win32:

--- functions

(defun my-frame-maximize () "Maximize Emacs window in win32" 
(interactive) 
(w32-send-sys-command ?\xf030))

(defun my-frame-restore () "Restore Emacs window in win32" 
(interactive) 
(w32-send-sys-command ?\xF120))

--- keys

(global-set-key [f2] 'my-frame-maximize) ; Maximize Emacs window
(global-set-key [C-f2] 'my-frame-restore) ; Restore Emacs window

---

It works as intended, but I wonder, is there any simple way to replace 
these two keys with a function that use only one key (f2) to toggle 
between these two states?

Thanks,
Johan