JS Liste déroul. en chaine qui se Masq/Démasq

<form action="" method="post">
<table>
<tr>
<td>Country: </td>
<td><select id="dhtmlgoodies_country" name="dhtmlgoodies_country" onchange="getStateList(this)">
<option>Any</option>
<?php
$sql = 'SELECT * FROM pays ORDER BY pays_int';
$query = mysql_query($sql) or die( 'Erreur' );
while ( $g = mysql_fetch_array( $query ))
{
echo '<option value="'.$g['id_pays'].'">'.$g['pays_int'].'</option>';
}
?>
</select>
</td>
</tr>
<tr id="dhtml_state" style="display:none">
<td>State:</td>
<td><select id="dhtmlgoodies_state" name="dhtmlgoodies_state" onchange="getCityList(this)"></select></td>
</tr>
<tr id="dhtml_city" style="display:none">
<td>City: </td>
<td><select id="dhtmlgoodies_city" name="dhtmlgoodies_city"></select></td>
</tr>
</table>
</form>

function getStateList(sel)
{
var countryCode = sel.options[sel.selectedIndex].value;
var sel_state = document.getElementById('dhtmlgoodies_state');
sel_state.options.length = 0; // Empty city select box
if(countryCode.length>0){
document.getElementById('dhtml_state').style.display = "";
var index = ajax.length;
ajax[index] = new sack();
ajax[index].requestFile = 'getCities.php?countryCode=' + countryCode; // Specifying which file to get
ajax[index].onCompletion = function(){ createState(index) }; // Specify function that will be executed after file has been found
ajax[index].runAJAX(); // Execute AJAX function
}
}
function getCityList(sel)
{
var stateCode = sel.options[sel.selectedIndex].value;
var sel_city = document.getElementById('dhtmlgoodies_city');
sel_city.options.length = 0; // Empty city select box
if(stateCode.length>0){
document.getElementById('dhtml_city').style.display = "";
var index = ajax.length;
ajax[index] = new sack();
ajax[index].requestFile = 'getCities.php?stateCode=' + stateCode; // Specifying which file to get
ajax[index].onCompletion = function(){ createCities(index) }; // Specify function that will be executed after file has been found
ajax[index].runAJAX(); // Execute AJAX function
}
}
function createState(index)
{
var obj = document.getElementById('dhtmlgoodies_state');
eval(ajax[index].response); // Executing the response from Ajax as Javascript code
}
function createCities(index)
{
var obj = document.getElementById('dhtmlgoodies_city');
eval(ajax[index].response); // Executing the response from Ajax as Javascript code
}