tab.Add(menuOpen.SizePos(),    "Open");
	tab.Add(menuConvert.SizePos(), "Convert");

	tab.WhenSet = [&] {
		PromptOK("Selected tab " + FormatInt(tab.Get()));
		if (tab.IsAt(menuOpen)) 
			PromptOK("At Open");
		else if (tab.IsAt(menuConvert)) 
			PromptOK("At Convert");
	};

TabCtrl::Item& tabOpen = tab.GetItem(tab.Find(menuOpen));
tabOpen.Enable(false);