Scroll Callback

Perhaps I read the LW documentation from the wrong perspective. When I
think of a callback responding to a scrolling action, this is what comes
to mind ... but it does not agree with me. I reckoned clicking the
scroll buttons would fire the callback:

(capi:contain 
 (make-instance   
  'capi:list-panel      
  :items '(:red :blue :green :yellow :orange :purple :pink :brown :tan)   
  :print-function 'string-capitalize   
  :scroll-callback
   #'(lambda (&rest args)
       (capi:display-message "Do something"))
  :max-height 25))

Sage advice needed!

Thanks,
Brian C.