To trap Alt+Tab you have to catch the message before the OS process it. A simple way to achieve it is to register Alt+Tab as a hotkey: BOOL CYourDlg::OnInitDialog() { ... m_nHotKeyID = 100; // Unique identifier of the new hotkey. BOOL m_isKeyRegistered = RegisterHotKey(GetSafeHwnd(), m_nHotKeyID, MOD_ALT, VK_TAB); ... } To process the hotkey PreTranslate WM_HOTKEY: BOOL CYourDlg::PreTranslateMessage(MSG* pMsg) { ... if((pMsg->message == WM_HOTKEY) && (pMsg->wParam == m_nHotKeyID)) MessageBox("Alt+Tab trapped"); .... } Remember to unregister it before existing the app: BOOL CYourDlg::OnDestroy() { ... UnregisterHotKey(GetSafeHwnd(), m_nHotKeyID); ... } Read Lock Windows Desktop[^], there are some references that shows it. I hope it helps, Marc Soleda. ... she said you are the perfect stranger she said baby let's keep it like this... Tunnel of Love, Dire Straits.
