求代码：如何实现从一个多值的select添加到另一个多值的select中

<html>
<head>
<META content="text/html; charset=gb2312" http-equiv=Content-Type>
</head>
<body bgColor=skyblue>
<form action="select.htm" method="post" name="myform">
  <br>
  <br>
  <br>
  <div align="center"> 
    <center>
      <left> 
      <table style="FONT-SIZE: smaller">
        <tr> 
          <td width="116"> 
            <table>
              <tr> 
                <td> 
                  <select name="left_select" style="HEIGHT: 200px; WIDTH: 100px" multiple>
                    <OPTION VALUE="A">A</OPTION>
                    <OPTION VALUE="B">B</OPTION>
                    <OPTION VALUE="C">C</OPTION>
                    <OPTION VALUE="D">D</OPTION>
                    <OPTION VALUE="E">E</OPTION>
                    <OPTION VALUE="F">F</OPTION>
                    <OPTION VALUE="G">G</OPTION>
                    <OPTION VALUE="H">H</OPTION>
                    <OPTION VALUE="I">I</OPTION>
                    <OPTION VALUE="J">J</OPTION>
                    <OPTION VALUE="K">K</OPTION>
                    <OPTION VALUE="L">L</OPTION>
                    <OPTION VALUE="M">M</OPTION>
                    <OPTION VALUE="N">N</OPTION>
                    <OPTION VALUE="O">O</OPTION>
                    <OPTION VALUE="P">P</OPTION>
                  </select>
                </td>
              </tr>
            </table>
          </td>
          <td width="43"> 
            <table border="0">
              <br>
              <tr> 
                <td> 
                  <INPUT language="javascript" name="btn_select_addany" onclick="fun_select_addany(document.myform)" style="COLOR: blue; FONT-FAMILY: Webdings; FONT-SIZE: 12pt; FONT-WEIGHT: normal; HEIGHT: 28px; WIDTH: 27px" title="Add any" type=button value="8">
                </td>
              </tr>
              <tr> 
                <td> 
                  <INPUT language="javascript" name="btn_select_addall" onclick="fun_select_addall(document.myform)" style="COLOR: blue; FONT-FAMILY: Webdings; FONT-SIZE: 12pt; FONT-WEIGHT: normal; HEIGHT: 28px; WIDTH: 27px" title="Add all" type=button value=: DESIGNTIMESP="17713">
                </td>
              </tr>
              <tr> 
                <td> <br>
                  <br>
                </td>
              </tr>
              <tr> 
                <td> 
                  <INPUT language="javascript" name="btn_select_dltany" onclick="fun_select_dltany(document.myform)" style="COLOR: blue; FONT-FAMILY: Webdings; FONT-SIZE: 12pt; FONT-WEIGHT: normal; HEIGHT: 28px; WIDTH: 27px" title ="delete any" type=button value="7">
                </td>
              </tr>
              <tr> 
                <td> 
                  <INPUT language="javascript" name="btn_select_dltall" onclick="fun_select_dltall(document.myform)" style="COLOR: blue; FONT-FAMILY: Webdings; FONT-SIZE: 12pt; FONT-WEIGHT: normal; HEIGHT: 28px; WIDTH: 27px" title ="delete all" type=button value="9">
                </td>
              </tr>
              <tr> 
                <td></td>
              </tr>
              <tr> 
                <td> </td>
              </tr>
            </table>
          </TD>
          <td width="119"> 
            <table style="FONT-SIZE: smaller">
              <tr> 
                <td> 
                  <select name="right_select" style="HEIGHT: 200px; WIDTH: 100px" multiple>
                  </select>
                </td>
              </tr>
            </table>
          </td>
  <td width="10">&nbsp; </td>
        </TR>
      </TABLE>
    </center>
  </div>
</form>
</body>
</html>
          
<script language="javascript">
function fun_select_addany(theform){
    var i; 
    for (i=0;i<theform.left_select.length;i++){
        if (theform.left_select.options[i].selected == true){
           theform.right_select.options[theform.right_select.length]=new Option(theform.left_select.options[i].text);
           theform.left_select.options.remove(i);
           i--;
        } 
    }
    sort_select(document.myform);
} function fun_select_addall(theform){
    var i;   
    for (i=0;i<theform.left_select.length;i++){
        theform.right_select.options[theform.right_select.length]=new Option(theform.left_select.options[i].text);    
    }
    theform.left_select.length=0;     
    sort_select(document.myform); 
}  function fun_select_dltany(theform){
   var i; 
   for (i=0;i<theform.right_select.length;i++){
       if (theform.right_select.options[i].selected == true){
          theform.left_select.options[theform.left_select.length]=new Option(theform.right_select.options[i].text);
          theform.right_select.options[i] =new Option("");
          theform.right_select.options.remove(i);
          i--;
       } 
   }
   sort_select(document.myform);
}function fun_select_dltall(theform){
    var i;   
    for (i=0;i<theform.right_select.length;i++){
        theform.left_select.options[theform.left_select.length]=new Option(theform.right_select.options[i].text);
    }
    theform.right_select.length=0;            
    sort_select(document.myform);
}
function sort_select(theform){
    var i; 
    var left_array= new Array();                
    for (i=0;i<theform.left_select.length;i++){
        left_array[i] = new Array(theform.left_select.options[i].text);
    } left_array.sort();   theform.left_select.length=0;          
    
    for (i=0;i<left_array.length;i++){
        theform.left_select.options[theform.left_select.length]=new Option(left_array[i]);
    }    left_array= new Array();  
}   
</script>