fill-list-box (object event)
    (when (char= [%KeyChar event] #\Return)
      (<a class=noborder href="#cast">cast</a> object "TextBox")
      (let* ((input-string [%Text object])
             (input-length (length input-string)))
        (when (plusp input-length)
          (let ((apropos-text
                  (with-output-to-string (*standard-output*)
                    (apropos input-string)))
                (list-box [$listBox (cast [%Parent object] "AproposControl")]))
            (setf [%Text list