// slider control
var slider = new Control.Slider('TagCloudSliderHandle', 'TagCloudSliderTrack', {
    axis: 'vertical',
	onSlide: function(v) { scrollTagCloud(v, $('TagCloudScrollable'), slider);  },
	onChange: function(v) { scrollTagCloud(v, $('TagCloudScrollable'), slider); }
	});	

// scroll the element based on its width and the slider maximum value
function scrollTagCloud(value, element, slider) {
	element.scrollTop = Math.round(value/slider.maximum*(element.scrollHeight-element.offsetHeight));
}