function vertical_img_scroll(){
  var SPEED_MS = 300;
  $$(".item_images_links > li > a").addEvent('click', function(e){
    this.getParent(".item_images_links").getElements("a").removeClass('current');
    this.addClass('current');
    var portfolio = this.getParent("div.item_entry");
    var box = portfolio.getElement("div.item_imagebox");
    var transition = new Fx.Transition(Fx.Transitions.Quad);
    var effect = new Fx.Scroll(box, {duration: SPEED_MS, transition: transition.easeOut});
    effect.toElement(box.getElement("img."+this.get("rel")));
    e.stop();
  });
}

window.addEvent('domready', function(){
 vertical_img_scroll(); 
});