var xmlHttp

function checkavail() {
	xmlHttp=GetXmlHttpObject();

	if (xmlHttp==null) {
		alert('Giving up :( Cannot create an XMLHTTP instance. Something is borked.');
		return;
	}

	var loc = document.getElementById('loc').value;
	var cid = document.getElementById('campid').value;

	var selectedArray = new Array();
	var selObj = document.getElementById('weeks');
	var i;
	var url = "checkavail.php?loc=" + loc + "&cid=" + cid + "&";
	for (i=0; i<selObj.options.length; i++) {
		if (selObj.options[i].selected) {
			url = url + "week" + i + "=" + selObj.options[i].value;
		}
	}
	url = url + "&" + Math.random();

	xmlHttp.onreadystatechange=  function() {
		if (xmlHttp.readyState==4) {
			document.getElementById('thesubmit').innerHTML=xmlHttp.responseText;
		}
	}
	xmlHttp.open("GET",url,true);
	xmlHttp.send(null);
}

function GetXmlHttpObject() {
	var xmlHttp=null;
	try {
		// Firefox, Opera 8.0+, Safari, IE7
		xmlHttp=new XMLHttpRequest();
	}
	catch (e) {
		// IE6 and under
		try {
			xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
		}
		catch (e) {
			xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
		}
	}
	return xmlHttp;
}