var step = 10;
var timerLeft, timerRight;

function scrollDivLeft(id, imageid) {
    document.getElementById(id).scrollLeft += step;
    timerLeft = setTimeout("scrollDivLeft('" + id + "','" + imageid + "')", 10);
}

function scrollDivRight(id, imageid) {
    document.getElementById(id).scrollLeft -= step;
    timerRight = setTimeout("scrollDivRight('" + id + "','" + imageid + "')", 10);
}