var tid=0;
var delaytime=10;   // time

var rowlength=1;  // 

function upscroll(who) {
  var obj = document.getElementById(who);
  obj.scrollTop-=rowlength;
  tid = setTimeout("upscroll('"+obj.id+"')",delaytime);
  if(obj.scrollTop <= 0 ) clearTimeout(tid);
}

function dnscroll(who) {
  var obj = document.getElementById(who);
  obj.scrollTop+=rowlength;
  tid = setTimeout("dnscroll('"+obj.id+"')",delaytime);
  if(obj.scrollTop >= obj.scrollHeight) clearTimeout(tid);
}