js 访问父框架中的frame，出现拒绝访问的错误，怎么解决

父页面：
<HTML>
<frameset cols="400,8,*" frameborder="1" border="1" framespacing="0" framepadding="0" id="topFrame"
style="border:0px solid #cccccc" >
<frame name='left' src='http://www.baidu.com' frameborder="0" ></frame> <frame name='center' src='newBank.htm' scrolling="no" frameborder="0" noresize></frame>
<frame name='right' src='http://www.baidu.com' frameborder="0" ></frame>
</frameset>
</HTML>

newBank.htm 中间页：
<HTML>
<head>
<!--<script language="javascript"
src="jquery.js"></script> -->
<script src="jquery.js" type="text/javascript"></script>
<SCRIPT LANGUAGE="JavaScript">
<!--
function downToResize(obj) {
// var myParent = parent.frames["left"];
// var myParent = parent.frames['left'];


obj.mouseDownX=event.clientX;
obj.parentLeftFW = parent.left.document.body.offsetWidth; // obj.parentLeftFW = parent.opener.document.body.offsetWidth;
// obj.parentLeftFW = document.getElementById("left").width;

obj.setCapture();
}
function moveToResize(obj){
if(!obj.mouseDownX) return false;
var changeW = event.clientX*1-obj.mouseDownX;
var newLeftW=obj.parentLeftFW*1+changeW;
if(newLeftW<=200) newLeftW = 200;
parent.parent.document.body.cols= newLeftW+',8,*';
}
function upToResize(obj){

obj.releaseCapture();
obj.mouseDownX=0;
obj.style.cursor = 'default';
}
//-->
</SCRIPT>
</head>
<div id='show' style="display:'inline';position:'absolute';z-index:5;border:'1px dotted red';width:'100px';height:'100px'"></div>
<body style='background-color:gray' onmousedown="downToResize(this);"
onmousemove="moveToResize(this);"
onmouseup="upToResize(this);" onmouseenter="this.style.cursor='col-resize';"
onmouseout="this.style.cursor='default';">
</body>
</HTML>


老是出现拒绝访问，我要实现的效果是随着中间的frame改变左右两个frame的宽度