defaultStep = 1;
step        = defaultStep;

function scrollDivDown(id){
  clearTimeout(timerDown);
  document.getElementById(id).scrollTop += step;
  timerDown = setTimeout("scrollDivDown('"+id+"')", 10);
}

function scrollDivUp(id){
  clearTimeout(timerUp);
  document.getElementById(id).scrollTop -= step;
  timerUp = setTimeout("scrollDivUp('"+id+"')", 10);
}

timerDown = "";
timerUp   = "";

function stopMe(){
  clearTimeout(timerDown);
  clearTimeout(timerUp);
}

document.onmousemove = function(){stopMe()};