XPCE Button message

[Rk]

% Author:

% Date: 02/04/2015

:- use_module(library(pce)).

:- use_module(code1).

dialog('screen1',

       [ object        :=

           Screen_,

         parts         :=

           [ Screen_ := dialog('Screen1'),

             Button1 := button(quit),

             Button2 := button(os2)

           ],

         modifications :=

           [ Button2 := [ label := 'openScreen2'],

             Button1 := [ label := 'quit']

             ],

         layout        :=

           [ area(Button2,area(60, 19, 89, 24)),

             area(Button1,area(60, 80, 80, 24))

           ],

         behaviour     :=

%Button 2 opens dialog screen2

           [ Button2 := [ message := message(dia_target_dialog(screen2))

                        ],

             Button1 := [ message := message(Screen_, destroy)

                        ]

           ]

        ]).

dialog('screen2',

       [ object        :=

           Screen_,

         parts         :=

           [ Screen_ := dialog('Screen2'),

             Button1 := button(back),

             Button2 := button(runCode)

           ],

         modifications :=

           [ Button2 := [ label := 'runCode'],

             Button1 := [ label := 'back']

           ],

         layout        :=

           [ area(Button2,area(146, 34, 80, 24)),

             area(Button1,area(148, 96, 80, 24))

           ],

%Button 1 goes back to dialog screen1

           behaviour     :=

           [ Button2 := [ message := message(@prolog,'code1')

                        ],

             Button1 := [ message := message(@prolog, '')

                        ]

           ]

       ]).

%quit(M):- send(M, button(quit,message(M, destroy))).

s_d :- make_dialog(M,screen1),

% make_dialog(N1,screen2),

%send(M,button(quit, message(M, destroy))),

send(M, open).

%make_dialog(M,screen2), send(M,open).

i have got the code running for destroy and running code.pl , 

i need help to navigate between dialogs on click on button.

button2, needs to open dialog screen2 , i cant figure out the message for this.

any help will be appreciated.