function initialiser_slider(nbr_pages, box_id, id_previous, id_next)
{

 var totIncrement = 0;
 var increment = 516;
 var maxRightIncrement = increment*(-nbr_pages);

 var fx = new Fx.Morph(box_id, {
    duration: 650,
    transition: Fx.Transitions.Back.easeInOut,
    wait: true
    });

//-------------------------------------
// EVENTS for the button "previous"
    $(id_previous).addEvents({
        'click' : function(event){
        if(totIncrement<0){
            totIncrement = totIncrement+increment;
            fx.start({'margin-left':totIncrement});
        }
        return false;
    }
});

//-------------------------------------
// EVENTS for the button "next"
$(id_next).addEvents({
    'click' : function(event){
    if(totIncrement>maxRightIncrement){
        totIncrement = totIncrement-increment;
        fx.start({'margin-left':totIncrement});
    }
    return false;
}
})

}