if($("slideLeft") && $("slideRight")) {
  Event.observe("slideLeft", "click", slide.bind(this, true));
  Event.observe("slideRight", "click", slide.bind(this, false));
  var bInProgress = false;
  var iWidth = $("slider").getWidth();
}

function slide(bLeft, event) {
  if(!bInProgress) {
    bInProgress = true;
    var iMarginLeft = parseInt($("slider").getStyle("margin-left"));

    if(bLeft && iMarginLeft < 0) {
      new Effect.Morph("slider", {style: "margin-left:"+(iMarginLeft+500)+"px", duration: 1, afterFinish: function() {bInProgress = false;}});
    } else if(!bLeft && (iMarginLeft*(-1)) < (iWidth-500)) {
      new Effect.Morph("slider", {style: "margin-left:"+(iMarginLeft-500)+"px", duration: 1, afterFinish: function() {bInProgress = false;}});
    } else {
      bInProgress = false;
    }
  }

  event.stop();
}