GUI can't read variable with setappdata and getappdata

I'm working on setappdata and getappdata. My program calls another function within function callback.

 function pushbutton1_Callback(hObject, eventdata, handles)
   hitung(handles)
   d=str2num(get(handles.edit3,'String'));
   c=getappdata(handles.pushbutton1,'c2');
   set(handles.edit4,'String',c);
 while c>d
   a=a-1;
   c=a/b;
   set(handles.listbox1,'String',c);
 end

 function hitung(handles)
   a=str2num(get(handles.edit1,'String'));
   b=str2num(get(handles.edit2,'String'));
   c=a/b;
   set(handles.listbox1,'String',c);
   setappdata(handles.listbox1,'c2',c);

I tried edit1 <6>, edit2 <3>, edit3 <1>. But variable c from <c=getappdata(handles.pushbutton1,'c2');> can't display in edit4, and because of that while loops can't run. So the result in listbox1 <2>. Is there any solution? Thankyou.