iframe中scrollbar的控制问题（有加分）

只能模拟滚动
<iframe id=ifrm src=ifrmtable.htm></iframe>ifrmtable.htm
<style>
.scrollarrow {
font-family: Webdings;
color: blue;
text-align: center;
cursor: hand;
background: transparent; 
}
</style>
<script>
function KB_keepItInIE(theName,theWantTop,theWantLeft) {
theRealTop=parseInt(document.body.scrollTop)
theTrueTop=theWantTop+theRealTop
document.all[theName].style.top=theTrueTop
theRealLeft=parseInt(document.body.scrollLeft)
theTrueLeft=theWantLeft+theRealLeft
document.all[theName].style.left=theTrueLeft
}setInterval('KB_keepItInIE("arrowup",0,document.body.offsetWidth-20)',1)
setInterval('KB_keepItInIE("arrowdown",document.body.offsetHeight-30,document.body.offsetWidth-20)',1)function divscroll(flag)
{
if(flag=="down")
document.body.scrollTop+=document.all.mytr.offsetHeight;
else
document.body.scrollTop-=document.all.mytr.offsetHeight;
}
</script>
<body style="overflow-y:hidden;overflow-x:hidden">
<div id=arrowup class=scrollarrow style="position: absolute; right: 10; top: 10; z-index: 4; overflow: hidden" onclick=divscroll("up")>5</div>
<div id=arrowdown class=scrollarrow style="position: absolute; right: 10; bottom: 10; z-index: 4; overflow: hidden" onclick=divscroll("down")>6</div>
<table id=mytable>
<tr id=mytr><td>bayern1</td><td>bayern1</td></tr>
<tr><td>bayern2</td><td>bayern2</td></tr>
<tr><td>bayern3</td><td>bayern3</td></tr>
<tr><td>bayern4</td><td>bayern4</td></tr>
<tr><td>bayern5</td><td>bayern5</td></tr>
<tr><td>bayern6</td><td>bayern6</td></tr>
<tr><td>bayern7</td><td>bayern7</td></tr>
<tr><td>bayern8</td><td>bayern8</td></tr>
<tr><td>bayern9</td><td>bayern9</td></tr>
<tr><td>bayern0</td><td>bayern0</td></tr>
</table>