[racket] Getting Handle

Hello friends,

I create and show a dialog like this:

(define (start-dialog)
(define dialog (new dialog% [label "Test"]))
(define msg (new message% [parent dialog]
                          [label "Kein Ereignis bisher"]))
(new button% [parent dialog]
             [label "Drück Mich!"]
             [callback (lambda (button event)
                         (send msg set-label "Drücken"))])
(send dialog show #t))

(define c1 (make-eventspace))
(define (show-message)
(parameterize ([current-eventspace c1])
             (thread start-dialog)))


How can I get the handle of the dialog. Or from a frame?

Yours,