The following code can be used to dynamically add, remove or select all items in a SELECT object.  The code assumes that when objects are added to the SELECT object, that the display text and value are identical. 

<script language="javascript"> 
   function addToList(txtBox, selectBox){ 
      var oOption = document.createElement("OPTION"); 
      oOption.text = txtBox.value; 
      oOption.value = txtBox.value; 
      selectBox.add(oOption); 
      txtBox.value = ""; 
      txtBox.focus(); 
   } 

   function removeFromList(selectBox){ 
      selectBox.remove(selectBox.selectedIndex); 
   } 

   function selectEntireList(selectBox){ 
      var fromObj = selectBox; 
      for ( selIndex = fromObj.length; selIndex -- ; selIndex > 0 ){ 
         if(fromObj.options[selIndex].text != ""){ 
            fromObj.options[selIndex].selected = true; 
         } 
      } 
   }
</script>