Linked dropdowns in registration

[menoutdoors]

Hello,

Im working on a registration system that has 2 linked dropdown lists. These lists are used to select Country then region (i.e. United States / New york). Now, the site is targeting a world wide audience so I need to have 200+ countries and in the range of 1500 regions. This makes having 2 seperate non linked dropdowns unrealistic.

I have the dropdowns coded on a normal php page but I am having issues getting them into the registration.php and associated template. At this point im using a combination of js , php , mysql to populate the 2nd dropdown after the onchange event.

Here is my php code.

<SCRIPT language=JavaScript>
function reload(form){
var val=form.cat.options[form.cat.options.selectedIndex].value; 
self.location='dropdown.php?cat=' + val ;
}
</script>

<?


///////// Getting the data from Mysql table for first list box//////////
$quer2=mysql_query("SELECT DISTINCT name,cc FROM country order by name"); 
///////////// End of query for first list box////////////

/////// for second drop down list we will check if category is selected else we will display all the subcategory///// 
//if(isset($cat) and strlen($cat) > 0){
if (isset($_GET['cat'])) {

//create mysql query
$regionlookup = "SELECT DISTINCT name FROM region WHERE cc='".$_GET['cat']."'"; 
$quer=mysql_query($regionlookup); 
}else{$quer=mysql_query("SELECT DISTINCT name FROM region order by name"); } 
////////// end of query for second subcategory drop down list box ///////////////////////////

echo "<form method=post name=f1 action=''>";
//////////        Starting of first drop downlist /////////
echo "<select name='cat' onchange=\"reload(this.form)\"><option value=''>Select one</option>";
while($noticia2 = mysql_fetch_array($quer2)) { 
if($noticia2['cc']==$_GET['cat']){echo "<option selected value='$noticia2[cc]'>$noticia2[name]</option>"."<BR>";}
else{echo  "<option value='$noticia2[cc]'>$noticia2[name]</option>";}
}
echo "</select>";
//////////////////  This will end the first drop down list ///////////

//////////        Starting of second drop downlist /////////
echo "<select name='subcat'><option value=''>Select one</option>";
while($noticia = mysql_fetch_array($quer)) { 
echo  "<option value='$noticia[name]'>$noticia[name]</option>";
}
echo "</select>";
//////////////////  This will end the second drop down list ///////////
echo "</form>";
?>

Is there anyway for me to incorporate this into the register.php script so that it will display these linked dropdowns during registration?

Thank you in advance.