function getChart() {
		var tud = document.CalculateOptions.tud.value;
		var mtp = document.CalculateOptions.mtp.value;
		var ir = document.CalculateOptions.ir.value;		
		var objID = "debtchart";
	    var obj = document.getElementById(objID);
		var serverPage = "calc.php?tud="+tud+"&mtp="+mtp+"&ir="+ir;
		var obj = document.getElementById(objID);
		xmlhttp.open("GET", serverPage);
		xmlhttp.onreadystatechange = function() {
		if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
		obj.innerHTML = xmlhttp.responseText;
		}
		}
		xmlhttp.send(null);
		}