MATLAB: Problem in retreiveng textbox string in uicontrol created dialog

MATLABuicontrol

Hello,
I have the following function, which creates a dialog with two textboxex (Textbox1 and Textbox2 and a checkbox). I would like two things to happen as I type text in Textbox 1:
  • toggle the checkbox
  • programatically copy the text from Textbox1 to Textbox2
Toggling the checkbox always works, however programatically copying the same text in Textbox 2 only works if I add a breakpoint in the Textbox_callback function. If I do not add this breakpoint, then Textbox2 will only display the "original text" text each time I change the text in Textbox1.
What am I doing wrong?
function choosedialog        
        d = dialog('Position',[300 300 250 200],'Name','Serial Number');
       
        Textbox1 = uicontrol('Parent',d,...
            'Style','edit',...
            'Position',[20 100 210 40],...
            'String','original text',...
            'KeyPressFcn',@Textbox_callback);
        
        ck1 = uicontrol('Parent',d,...
            'Style','checkbox',...
            'Position',[20 150 210 40],...
            'String','Checkbox');
        
         Textbox2 = uicontrol('Parent',d,...
            'Style','edit',...
            'Position',[20 40 210 40],...
            'String','');
        
        %focus automatically on textbox
        uicontrol(Textbox1);
       
        % Wait for d to close before running to completion
        uiwait(d);
       
        function Textbox_callback(Textbox1,event)
            ck1.Value = ~ck1.Value;
            Textbox2.String = Textbox1.String;
        end
end
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