defaultStep=10
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()}