emacs calculator

[B.T. Raven]

I added the following lines to my .emacs (i386-mingw: 21.3.1):

(autoload 'calculator "calculator"
    "Run the Emacs calculator." t)
  (global-set-key [(control return)] 'calculator)

After saving this, exiting, restarting, still no go. C-h k C-return is
shown as undefined.

Then I replaced the last line with:
(define-key global-map [(control return)] 'calculator)

Same result. What I am I doing wrong?

Thanks,

Ed