How to change uicontrol properties in a callback function of a different uicontrol?

Hi everyone! I'm developing a GUI in which I would like to make invisible a popupmenu when every value is choosed by another popupmenu. The code is the follow:

    popupmenu = uicontrol('style','popupmenu','string',{'A';'B'},'Callback',@pushbutton3_callback);
    rule_1a = uicontrol('style','popupmenu','string',{'C';'D'},'Callback',@pushbutton_callback);

    function pushbutton3_callback(hObject,event)
             set(rule_1a,'Visible','off')
    end

It doesn't work. How Can I do that? Many thanks!

Regards,

Adriano