void CMainFrame::OnToolbarDropDown(NMTOOLBAR* pnmtb, LRESULT *plr)
 {
    // load and display popup menu
    CMenu menu;
    menu.LoadMenu(IDR_FILEDROPDOWN);
    CMenu* pPopup = menu.GetSubMenu(0);
    ASSERT(pPopup);
 
    CRect rc;
    m_wndToolBar.SendMessage(TB_GETRECT, pnmtb->iItem, (LPARAM)&rc);
    m_wndToolBar.ClientToScreen(&rc);
 
    pPopup->TrackPopupMenu(TPM_LEFTALIGN|TPM_LEFTBUTTON|TPM_VERTICAL,
       rc.left, rc.bottom, this, &rc);
 }