Move items js help

Hi guyz.
The current version works fine… And I was not able to make two things on this js.
First one, if there is a same item on the boxes, the js must not move over item.(no duplicates on boxes)
Second, if the move item is " All", the right box must not contain other items. Else move item is other than " All" then right box must not have " All"

Your help appreciated.


<style>
select { width: 200px; float: left; } 
#Toolbar { width: 50px; float: left; text-align: center; padding-top: 30px; } 
#Toolbar input { width: 40px; }
</style>
<script>
function Move(inputControl) 
{ 
  var left = document.getElementById("Left"); 
  var right = document.getElementById("Right"); 
  var from, to; 
  var bAll = false; 
  switch (inputControl.value) 
  { 
  case '<<': 
    bAll = true; 
    // Fall through 
  case '<': 
    from = right; to = left; 
    break; 
  case '>>': 
    bAll = true; 
    // Fall through 
  case '>': 
    from = left; to = right; 
    break; 
  default: 
    alert("Check your HTML!"); 
  } 
  for (var i =from.length-1; i >=0; i--) 
  { 
    var o = from.options[i]; 
    if (bAll || o.selected) 
    { 			
			from.remove(i); 
			try 
			{
			to.add(o, null);  // Standard method, fails in IE (6&7 at least) 
			} 
			catch (e) 
			{ 
			to.add(o); // IE only 
			} 
		}	
  } 
}
</script>
<title>Untitled Document</title>
</head>

<body>

<select id="Left" multiple="multiple" size="10"> 
  <option value=" All"> All</option> 
  <option value="BK">BK</option> 
  <option value="QN">QN</option> 
	<option value="SI">SI</option> 
</select> 
 
<div id="Toolbar"> 
  <input type="button" value=">" onclick="Move(this)"/> 
  <input type="button" value=">>" onclick="Move(this)"/> 
  <input type="button" value="<<" onclick="Move(this)"/> 
  <input type="button" value="<" onclick="Move(this)"/> 
</div> 
 
<select id="Right" multiple="multiple" size="10"> 
<option value="SI">SI</option>
</select>
</body>


Hello!!Any help?