大家帮我看一下JS代码

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3c.org/TR/1999/REC-html401-19991224/loose.dtd">
<HTML xmlns="http://www.w3.org/1999/xhtml"><HEAD><TITLE>365Map</TITLE>
<META http-equiv=Content-Type content="text/html; charset=gbk">
<script type="text/javascript" src="http://map.api.365ditu.net/rmap1_0/rapi/rglobal/rheader.js"></script>
<META content="MSHTML 6.00.2900.5945" name=GENERATOR></HEAD>
<BODY onload=load()>
<DIV id=mapdiv 
style="POSITION: relative; width: 100%; height: 450px"></DIV>
<SCRIPT type=text/javascript>
    importClass('rapi.rwidget.rmap.RMap');
</SCRIPT><SCRIPT type=text/javascript>
var x1="";
var y1="";  
var html ="asdasda";
var h2 = "1111111";
var x="124.39812"
var y="40.133399"
function openLayer(conId,Name){
  x1=conId;
  y1=Name;
// document.write(x1);
// document.write(y1);
load();

}Maplet = null;
BigboxMarker = null;
function load(){
    Maplet = new RMap(0,0,900,500,y,x,9,IMG_SERVER+'/rt/mapdb/');
document.getElementById("mapdiv").appendChild(Maplet.get());
var toolbox=Maplet.getToolBox(JS_SERVER+'/rapi/rwidget/rmap/toolbox/');
toolbox.addCross();
addBigboxMarker() ;
 Maplet.show();
 if ((x1!="")&&(y1!=""))
 {
window.setTimeout(function smoothMove(){Maplet.dynSmoothMove(y1,x1,2);},5000)  }  
}function addBigboxMarker(){
    //if(BigboxMarker==null){
        BigboxMarker=Maplet.addBalloonMarker(
            new RLatLng(y,x),
            1000,'images/car.ico',
            html,
            h2,
            html);
        Maplet.refreshMarkers();
   
    //}
}
</SCRIPT>
<a href="javascript:openLayer('126.657717','45.773325');" >哈尔滨</a>
<a href="javascript:openLayer('116.409','39.918');" target="_self" >北京</a>
<a href="javascript:openLayer('123.432791','41.808645');" >沈阳</a>
<a href="javascript:openLayer('121.487899','31.249162');" >上海</a>
<a href="javascript:openLayer('118.778074','32.057236');" >南京</a>
<a href="javascript:openLayer('113.30765','23.120049');" >广州</a>
<a href="javascript:openLayer('114.025974','22.546054');" >深圳</a>
<a href="javascript:openLayer('106.530635','29.544606');" >重庆</a>
<a href="javascript:openLayer('108.953098','34.2778');" >西安</a>
</BODY></HTML>
刚打开显示的是默认的一个城市
我通过点击下面的城市列表想切换到另一城市
但是一点击就又出来一个地图了，怎么写能在原地图基础上改变城市呢？