How can I handle combobox notifications in a CGXComboBoxWnd derived class?

This can be done by overriding the OnCommand( ) method.

Example:

BOOL CMyComboBoxWnd::OnCommand(WPARAM wParam, LPARAM lParam)
{
#if _MFC_VER < 0x0300
   UINT nNotification = HIWORD(lParam);
   HWND hCtl = (HWND) LOWORD(lParam);
#else
   UINT nNotification = HIWORD(wParam);
   HWND hCtl = (HWND) lParam;
#endif
   if (hCtl == m_hWnd)     // is it really this wnd?
   {
      if (nNotification == CBN_SELCHANGE)
      {
         TRACE("Dropdown list changed\n");
      }
   }
   return CGXComboBoxWnd::OnCommand(wParam, lParam);
}