var scrollLeftTimer = null;
var scrollRightTimer = null;
var scrollIncrement = 3;
var scrollInterval = 10;

function startScrollLeft() {
  if (scrollLeftTimer == null) {
    scrollLeftTimer = setInterval("doScrollLeft();", scrollInterval);
  }
}

function stopScrollLeft() {
  clearInterval(scrollLeftTimer);
  scrollLeftTimer= null;
}

function doScrollLeft() {
   var divMain = document.all("divMain");
   if (divMain != null) {
     if (divMain.scrollLeft > 0) {
       divMain.scrollLeft -= scrollIncrement;
     }
   } else {
     alert("No divMain"); 
   }
}


function startScrollRight() {
  if (scrollRightTimer == null) {
    scrollRightTimer = setInterval("doScrollRight();", scrollIncrement);
  }
}

function stopScrollRight() {
  clearInterval(scrollRightTimer);
  scrollRightTimer= null;
}

function doScrollRight() {
   var divMain = document.all("divMain");
   if (divMain != null) {
     divMain.scrollLeft += scrollIncrement;
   } else {
     alert("No divMain"); 
   }
}