marquee怎么动态改变滚动方向
如题,我用javascript写的document.all.marquee.Direction= "up ";为什么不起作用还是向左边滚动

------解决方案--------------------
//用按钮控制字幕(marquee)的属性
<marquee id=mm direction= "right " scrolldelay= "70 " scrollamount= "6 "> meizz </marquee> <br>
<input type=button value=加速 onclick= "add() ">
<input type=button value=减速 onclick= "sub() ">
<input type=button value=right onclick= "e.direction= 'right ' ">
<input type=button value=left onclick= "e.direction= 'left ' ">
<input type=button value=up onclick= "e.direction= 'up ' ">
<input type=button value=down onclick= "e.direction= 'down ' ">
<script language= "JavaScript "> <!--
var e = document.getElementById( "mm ");
function add()
{
var n = 10;
if(e.scrollDelay-n > 0)
e.scrollDelay -= n;
e.scrollAmount += 1;
}
function sub()
{
if(e.scrollAmount > 0)
e.scrollAmount -= 1;
e.scrollDelay += 10;
}
//--> </script>