ButtonMouseDown プロパティ

// The client event ButtonMouseDown takes two parameters sender and e
// sender  is the object which is raising the event
// e is the SliderButtonMouseEventArgs

  function WebSlider1_ButtonMouseDown(sender, e) {

      var slider = $find("WebSlider1");

      //Gets the slider value
      var value = slider.getValue(0);

      //Checks which button is involved in the event.
      //True for minus button and false for plus button.
      var button = e.isMinus();

      if (button == true) {
          window.status = "Minus button is clicked";
      }
      else {
          window.status = "Plus button is clicked";
      }

  }