Hi all! I have written an Excel COM Add-In in C++ for automation of Excel with VBA. It contains an own dialog showing some general informations about the Add-In. Now i create a button in Excel that opens the dialog. Leaving the dialog with the escape key leads to an Excel message that the script is being interrupted instead of just closing the dialog. I could suppress the interruption message with: Application.EnableCancelKey = xlDisabled But that seems not to be the solution as the script can not be interrupted any more. Here is an example how i use VBA to open the dialog: Private Sub ShowAboutDialog_Click() Dim oComAddIn As COMAddIn Set oComAddIn = Application.COMAddIns.Item("MyComAddIn.Example") oComAddIn.Connect = True Call oComAddIn.Object.ShowAboutDlg End Sub My guess is that the problem is somewhere in the message handler of the dialog: INT_PTR CALLBACK CAboutDialog::AboutDlg( HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam) { switch(uMsg) { ... case WM_COMMAND: if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL) { // Here, the ESCAPE key should also be trapped? EndDialog(hwndDlg, LOWORD(wParam)); return TRUE; } ... } return FALSE; } The Dialog is created with: DialogBox(g_hModule, MAKEINTRESOURCE(IDD_ABOUT), hWndParent, (DLGPROC)AboutDlg) Thanks a lot!