var a=0;

  function scrollTop(s)
{
    var b=a+s;
  document.getElementById('dock').scrollTop=b;
  a=b;
    if(b==document.getElementById('dock').scrollHeight) {
        clearInterval(t);
    }

}
  function scrollBottom(s)
{
    var b=a-s;
  document.getElementById('dock').scrollTop=b;
  a=b;
  if(b==0) {
        clearInterval(t);
    }
}

  function goRight(s)
{
t=setInterval('scrollBottom(2);',20);
}
  function goLeft(s)
{
t=setInterval('scrollTop(2);',20);
}