var slideMax = $('pb_list').className - 730;

var slider = new Control.Slider('handle_middle','feature_slider', {
  onSlide: function(v){
    $('scrollable').scrollLeft = v * slideMax;
  },
  onChange: function(v){
    $('scrollable').scrollLeft = v * slideMax;
  }
});
$('handle_left').onclick = function() {
  slider.setValue(slider.value - 0.2);
}
$('handle_right').onclick = function() {
  slider.setValue(slider.value + 0.2);
}