tab.WhenSet = [&] {
		PromptOK("Selected tab " + FormatInt(tab.Get()));

		if (tab.IsAt(a1)) {
			PromptOK("At a1");
			menu.Set(THISBACK1(MainMenu, 1));
		} else if (tab.IsAt(a2)) {
			PromptOK("At a2");
			menu.Set(THISBACK1(MainMenu, 2));
		}
	};

...		

void Blam::MainMenu(Bar& bar, int num) {
	bar.Sub(Format(t_("Cookie %d"), num), [=](Bar & bar, int num) {
		bar.Add(Format(t_("Eat cookie %d"), num), THISBACK1(func, num));
	});
}