How to update modelines of all displayed buffers

[Cecil Westerhof]

I have defined the following function:
    (defun buffer-update-mode-line ()
      (setq buffer-mode-line (buffer-mode-line-extra))
      (force-mode-line-update t))

The function buffer-mode-line-extra gives the extra data I want to
display in the modeline.

It is called every minute with:
    (run-with-timer 60 60 'buffer-update-mode-line)

With this only the modeline of the current buffer is updated. In
principal (force-mode-line-update t) makes all modelines updated, but
that will only work if for every (visible) buffer buffer-mode-line is
updated with the function buffer-mode-line-extra. Is there a way to get
this done?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof