GUI button

I would like to know if i want to add a CEGUI button in Demo4,

I just put

CEGUI::PushButton* quitButton = (CEGUI::PushButton*)CEGUI::WindowManager::getSingleton().createWindow("TaharezLook/Button", (CEGUI::utf8*)"Quit");
sheet->addChildWindow(quitButton);
quitButton->setPosition(CEGUI::Point(0.35f, 0.45f));
quitButton->setSize(CEGUI::Size(0.3f, 0.1f));
quitButton->setText("Quit");

inside the createScene() method?

but it's not working.. please help