求js三级问题，每级都有默认值

Question

<TABLE cellSpacing=0 cellPadding=0 width=328 border=0 bgcolor="#EEEEEE">
 <form name="customize" method="post" target="weather" action=""  >
<TBODY>
<TR>
<TD height=4></TD></TR>
<TR>
<TD>
&nbsp;&nbsp;
</TD></TR>
<TR>
<TD>
<SCRIPT language=JavaScript> <!--
var g_selProvince;
var g_selCity;
var Provinces=new Array(
new Array("110000","北京市"),
new Array("440000","广东省"),
new Array("820000","澳门")
);var Citys=new Array(
new Array("110100","北京"),
new Array("440101","广州"),
new Array("440102","东莞"),
new Array("440103","清远"),
new Array("440104","顺德"),
new Array("440105","深圳"),
new Array("440106","中山"),
new Array("440107","惠州"),
new Array("440108","云浮"),
new Array("440109","珠海"),
new Array("440110","江门"),
new Array("440111","汕尾"),
new Array("440112","汕头"),
new Array("440113","佛山"),
new Array("440114","揭阳"),
new Array("440115","湛江"),
new Array("440116","茂名"),
new Array("440117","潮州"),
new Array("440118","韶关"),
new Array("440119","阳江"),
new Array("440120","河源"),
new Array("440121","梅州"),
new Array("440122","肇庆"),
new Array("440123","潮阳"));
function FillCitys(selCity,ProvinceCode)
{
        if(ProvinceCode=="110000"||ProvinceCode=="120000"||ProvinceCode=="310000"
                 ||ProvinceCode=="810000"||ProvinceCode=="820000"||ProvinceCode=="500000")
             count=0;
        else
                {selCity.options[0]=new Option("选择城市",ProvinceCode);
                count=1;}
                
    for(i=0;i<Citys.length;i++)
    {
        if(Citys[i][0].toString().substring(0,2)==ProvinceCode.substring(0,2))
        {
            selCity.options[count]=new Option(Citys[i][1],Citys[i][0]);
            if (selCity.options[count].value == '440102') {
                selCity.options[count].selected = true;
            }
            count = count + 1;
        }
    }    selCity.length=count;
}function Province_onchange()
{
    FillCitys(g_selCity,g_selProvince.value);
}function InitCitySelect(selProvince,selCity)
{
    g_selProvince=selProvince;
    g_selCity=selCity;
    selProvince.onchange=Function("Province_onchange();");
    FillProvinces(selProvince);
    Province_onchange();
}function FillProvinces(selProvince)
{
    selProvince.options[0]=new Option("选择省份","000000");
    for(i=0;i<Provinces.length;i++)
    {
        selProvince.options[i + 1] = new Option(Provinces[i][1], Provinces[i][0]);
        if (selProvince.options[i].value == '440000') {
            selProvince.options[i].selected = true;
        }
    }
    selProvince.length = i + 1;} //-->
</script> 
         <SELECT id="province" style="WIDTH: 100px" name=province>
             <option>省份</option>        
          </SELECT>
          <SELECT id="city" style="WIDTH: 100px" name=city>
             <option>城市</option>
          </SELECT>
 <SCRIPT language=javascript>
  InitCitySelect(document.customize.province,document.customize.city);
  </SCRIPT>
</TD></TR></TBODY>
</form>
</TABLE>以上为二级联动，且可以默认。现想一级，三级：加县级var Aares = new Array(
new Array("441901", "莞城区"),
new Array("441902", "东城区"),
new Array("441903", "南城区"),
new Array("441904", "万江区"),
new Array("441905", "虎门镇")
);
求高手指导