SET-PUSH-BUTTON-SENSITIVITY
===========================

syntax: (set-push-button-sensitivity 
           <babylon-push-button> <T | NIL>)

This function defines whether the button appears
sensitive or insensitive. The default value is T
(sensitive).

example: >(define-task SENSITIVE-DEMO-TASK (interface)
             :documentation "This is a demo"
             actions
             (set-push-button-sensitivity)
             (get-window-element interface "pb1") nil)
             (kb-notify "The push-button is
             insensitive ?~%")
             (set-push-button-sensitivity)
             (get-window-element interface "pb1") t)
             (kb-notify "The push-button is sensitive 
             ?~%")