var ajax = new sack();
var tnb ;
function getCityList(sel, nb)
{
  tnb = nb;
	var countryCode = sel.options[sel.selectedIndex].value;
	document.getElementById('clas'+ nb).options.length = 0;	// Empty city select box
	if(countryCode.length>0){
		ajax.requestFile = 'clas.php?countryCode='+countryCode;	// Specifying which file to get
		ajax.onCompletion = createCities;	// Specify function that will be executed after file has been found
		ajax.runAJAX();		// Execute AJAX function
	}
}

function createCities()
{
	var obj = document.getElementById('clas' + tnb );
	eval(ajax.response);	// Executing the response from Ajax as Javascript code	
}