disable ALT+CTRL+DEL!!!!

[phillip_Qt]

Hi All
i need a help. I wrote an application to lock the keyboard and mouse input. Its working fine, but ALT+CTRL+DEL key is working i need to disable this also. can any body help me. Below i've posted the code.

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::lock()
{
    QApplication::setOverrideCursor();
    QWidget::grabMouse();
    QWidget::grabKeyboard();
 
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow)
{
    ui->setupUi(this);

}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::lock()
{
    QApplication::setOverrideCursor();
    QWidget::grabMouse();
    QWidget::grabKeyboard();
 
}

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NB: i'm calling lock() inside main() function. Plz help me.