<SELECT onchange=JavaScript:showSubOpt(OptTrade,this,theform.SubTrade) name=Trade> 
        <OPTION value=""></OPTION> 
        <SCRIPT language=javascript>showMainOpt(OptTrade);</SCRIPT>
      </SELECT>&nbsp;
     <SELECT name=SubTrade></SELECT>
    <script language="javascript">
    [color=000080]SelectEd(document.theform.Trade,2000);[/color]   这个能显示出来           showSubOpt(OptTrade,this,theform.SubTrade)
    [color=FF0000]SelectEd(document.theform.SubTrade,2001);[/color]    为什么这个显示不出来呢
   </script>
function showSubOpt()
{    
    //OptTrade,this,theform.SubTrade
    var i,len,start,step,s1,s2,a,args=showSubOpt.arguments;
    var mainVal,val,name;
    a=args[0];
    s1=args[1];
    s2=args[2];
    start=0;
    step=2;
    IsAll = (args.length>=4)?args[3]:false;
    len=a.length;
    mainVal=s1.options[s1.selectedIndex].value;
    mainVal=mainVal.substr(0,2);

    for(i=s2.length-1;i>=0;i--)
    {
        s2.options[i]=null;
    }

    if(Number(mainVal)!=0)
    {
        for(i=start;i<len;i+=step)
        {
            val = a[i];
            name = a[i+1];
            if(val.substr(0,2)==mainVal && (IsAll || !IsAll && (val.substr(val.length-2) != "00")))
            {
                    s2.options[s2.length]=new Option(name,val,false,false);
            }
        }
    }
}