submenu->AppendSeparator();
submenu->Append(PU_SUB2, wxT("Another submenu"));
menu->Append(PU_SUBMAIN, wxT("Submenu"), submenu);
submenu->AppendSeparator();
submenu->Append(PU_SUB2, wxT("Another submenu"));
menu->Append(PU_SUBMAIN, wxT("Submenu"), submenu);