line length control setting

[Adam Hardy]

Hi All,
I am using a brute force method of stopping myself from writing long 
lines of code, using this in my .emacs:

(defun my-dont-insert-after-fill-column (&rest x)
  (when (> (current-column)
           fill-column)
    (delete-char -1)
    (beep)))

(add-hook 'after-change-functions 'my-dont-insert-after-fill-column)

But I discovered this is also acting on the command buffer, so I cannot 
add more than my fill column when doing simple file copies or renames or 
text search & replaces.

Is there a way that I can adapt my function above to stop it applying to 
the command buffer?

Thanks
Adam

--
GNU Emacs 21.3.1 on Linux 2.4.20 RH9