图片替换滚动条

<script language="JavaScript">
function mov(a){
scrollx = new_date.document.body.scrollLeft;
scrolly = new_date.document.body.scrollTop;
scrolly = scrolly + a;
new_date.window.scroll(scrollx,scrolly);
}
</script>

<table height="100" cellspacing="0" cellpadding="0" width="500" border="0">
<tr>
<td width="300"><iframe name="new_date" src="xxx.htm" width="100%" height="100" border="0" frameborder="no" marginwidth="0" marginheight="0" scrolling="no"></iframe></td>
<td>
<p><input type="button" value="↑" onMouseDown="mov(-40);"></p>
<p>&nbsp;</p>
<p><input type="button" value="↓" onMouseDown="mov(40);"></p>
</td>
</tr>
</table>