Listbox Move Left/Right Options using javascript

<table>
<tbody><tr>
    <td>
<select id="sourceSelect" size="10" multiple="">
 <option value="a">Afghanistan</option>
 <option value="b">Bahamas</option>
 
 <option value="d">Belgium</option>
 <option value="e">Bhutan</option>
 <option value="f">China</option>
 <option value="g">Croatia</option>
 <option value="h">Denmark</option>
 <option value="i">France</option>
</select>
    </td>
    <td>
        <button onclick="listboxMoveacross('sourceSelect', 'destSelect');">&gt;&gt;</button>  <br>
        <button onclick="listboxMoveacross('destSelect', 'sourceSelect');">&lt;&lt;</button>
    </td>
    <td>
<select id="destSelect" size="10" multiple="">
 <option value="a">Afghanistan</option>
 <option value="b">Bahamas</option>
 <option value="c">Barbados</option>
 <option value="d">Belgium</option>
 <option value="e">Bhutan</option>
 <option value="f">China</option>
 <option value="g">Croatia</option>
 <option value="h">Denmark</option>
 <option value="i">France</option>
<option value="c">Barbados</option></select>
    </td>
</tr>
</tbody></table>

    <script>
function listboxMoveacross(sourceID, destID) {
    var src = document.getElementById(sourceID);
    var dest = document.getElementById(destID);

    for(var count=0; count < src.options.length; count++) {

        if(src.options[count].selected == true) {
                var option = src.options[count];

                var newOption = document.createElement("option");
                newOption.value = option.value;
                newOption.text = option.text;
                newOption.selected = true;
                try {
                         dest.add(newOption, null); //Standard
                         src.remove(count, null);
                 }catch(error) {
                         dest.add(newOption); // IE only
                         src.remove(count);
                 }
                count--;
        }
    }
}
</script>