Related select in Magento how I do - magento

Question

It's possibile, in Magento, create two or more related select?
For example Country / Region
I try with jQuery but seem doesn't work.
Best Regards
I try with this code: in Mymodule output
app/design/frontend/base/default/template/mymodule/mymodule.phtml
<div id="continenti">
<?php
include_once 'option.class.php';
$obj = new Option();
$obj->ShowContinenti();
?>
</div>
<div id="nazioni">
Seleziona una nazione:<br>
<select id="sel_nazioni" name="sel_nazioni"><option value="no">Scegli...</option>
</select>
</div>
<div id="result"></div>
In my app/design/frontend/base/default/template/page/html/head.phtml
<script type="text/javascript" src="./jquery/jquery-1.3.2.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#sel_continenti').change(function(){
var cont = $('#sel_continenti').attr('value');
$.post("selection.php", {id_cont:cont}, function(data){
$("#sel_nazioni").empty();
$("div#result").empty();
$("#sel_nazioni").prepend(data);
});
});
$('#sel_nazioni').change(function(){
var id_naz = $('#sel_nazioni').attr('value');
$.post("result.php", {id:id_naz}, function(data){
$("div#result").empty();
$("div#result").prepend(data);
});
});
});
</script>
In my app/code/local/frontname/mymodule/sql/mysql4-install-0.1.0
<?php
$installer = $this;
$installer->startSetup();
$installer->run("
-- DROP TABLE IF EXISTS {$this->getTable('continenti')};
CREATE TABLE {$this->getTable('continenti')}
`id` INT(2) UNSIGNED NOT NULL AUTO_INCREMENT,
`continente` VARCHAR(40) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ;
INSERT INTO `continenti` (`id`, `continente`) VALUES
(1, 'Europa'),
(2, 'Africa'),
(3, 'Sud America');
-- DROP TABLE IF EXISTS {$this->getTable('nazioni')};
CREATE TABLE {$this->getTable('nazioni')}
`id` INT(3) UNSIGNED NOT NULL AUTO_INCREMENT,
`id_cont` INT(2) UNSIGNED NOT NULL,
`nazione` VARCHAR(50) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=14 ;
INSERT INTO {$this->getTable('nazioni')} (`id`, `id_cont`, `nazione`) VALUES
(1, 1, 'Spagna'),
(2, 1, 'Francia'),
(3, 1, 'Italia'),
(4, 1, 'Germania'),
(5, 1, 'Belgio'),
(6, 2, 'Egitto'),
(7, 2, 'Marocco'),
(8, 2, 'Tunisia'),
(9, 2, 'Uganda'),
(10, 3, 'Argentina'),
(11, 3, 'Cile'),
(13, 3, 'Brasile');
")
;
$installer->endSetup();
File result.php
<?php
include_once 'option.class.php';
$obj = new Option();
$obj->ShowResult();
?>
File selection.php
<?php
include_once 'option.class.php';
$obj = new Option();
$obj->ShowNazioni();
?>
The first select appear with the content of Region Table but, if I click and choise one region, the second select doesn't load data inside itself.
EDIT: resolved!
I change my head.phtml in
<script type="text/javascript" src="./jquery/jquery-1.3.2.js"></script>
<script type="text/javascript">
jQuery(document).ready(function() {
jQuery('#sel_continenti').change(function(){
var cont = jQuery('#sel_continenti').attr('value');
jQuery.post("selection.php", {id_cont:cont}, function(data){
jQuery("#sel_nazioni").empty();
jQuery("div#result").empty();
jQuery("#sel_nazioni").prepend(data);
});
});
jQuery('#sel_nazioni').change(function(){
var id_naz = jQuery('#sel_nazioni').attr('value');
jQuery.post("result.php", {id:id_naz}, function(data){
jQuery("div#result").empty();
jQuery("div#result").prepend(data);
});
});
});
</script>
I change $ with jQuery word!

Answer 1

Magento already has this kind of selects in checkout addresses phtmls, just that it uses Prototype.
<div class="field">
<label for="billing:region_id" class="required"><em>*</em><?php echo $this->__('State/Province') ?></label>
<div class="input-box">
<select id="billing:region_id" name="billing[region_id]" title="<?php echo $this->__('State/Province') ?>" class="validate-select" style="display:none;">
<option value=""><?php echo $this->__('Please select region, state or province') ?></option>
</select>
<script type="text/javascript">
//<![CDATA[
$('billing:region_id').setAttribute('defaultValue', "<?php echo $this->getAddress()->getRegionId() ?>");
//]]>
</script>
<input type="text" id="billing:region" name="billing[region]" value="<?php echo $this->escapeHtml($this->getAddress()->getRegion()) ?>" title="<?php echo $this->__('State/Province') ?>" class="input-text <?php echo $this->helper('customer/address')->getAttributeValidationClass('region') ?>" style="display:none;" />
</div>
<div class="field">
<label for="billing:country_id" class="required"><em>*</em><?php echo $this->__('Country') ?></label>
<div class="input-box">
<?php echo $this->getCountryHtmlSelect('billing') ?>
</div>
var billingRegionUpdater = new RegionUpdater('billing:country_id', 'billing:region', 'billing:region_id', <?php echo $this->helper('directory')->getRegionJson() ?>, undefined, 'billing:postcode');