window.addEvent('domready', function(){
// Declaring increment vars
var totIncrement = 0;
var increment = 183;
var maxRightIncrement = increment*(-7);
var slideBoxs = $('slider-list');
// FX var
var fx = new Fx.Tween(slideBoxs, {duration: 500, transition: 'back:in:out'});

    $('previous').addEvent('click', function() {
        if(totIncrement < 0) {
            totIncrement += increment;
            fx.start('margin-left', totIncrement);
        }
    });

    $('next').addEvent('click', function() {
        if(totIncrement > maxRightIncrement) {
            totIncrement -= increment;
            fx.start('margin-left', totIncrement);
        }
    });

});