Slider : MouseLeftButtonDown event

Constructor :

mediaSlider.AddHandler(FrameworkElement.MouseLeftButtonDownEvent, new MouseButtonEventHandler(mediaSlider_MouseLeftButtonDown), true);

Event handler :

private void mediaSlider_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
txt.Text ="MouseLeftButton DOWN";
}

http://forums.silverlight.net/forums/p/117368/264314.aspx