var xmlHttp

function GetXmlHttpObject()
{ 
var objXMLHttp=null
if (window.XMLHttpRequest)
{
objXMLHttp=new XMLHttpRequest()
}
else if (window.ActiveXObject)
{
objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
}
return objXMLHttp
}


function CalculateRepayment(given_form){
	var loanamount= given_form.mortg_amount.value;
    	var interest= given_form.interest_amount.value;
	var term =getmenuvalue(given_form.mortg_term);
	var cookie_id = given_form.cid.value;
	var I= interest/12;
	var X=1/(1+I/100);
	var N= term *12;
	given_form.txtrepay.value = formatnumber(loanamount*(X-1)/(Math.pow(X,N+1)-X));
	given_form.txtinterest.value=formatnumber((loanamount-loanamount*Math.pow(X,N))*(X-1)/(Math.pow(X,N+1)-X));

	xmlHttp=GetXmlHttpObject()
	if (xmlHttp==null)
	{
		alert ("Browser does not support HTTP Request");
		return;
	} 

	var url="update_calc.php";
	url=url+"?cookie_id="+cookie_id+"&loanamount="+loanamount+"&term="+term+"&interest="+interest;
	xmlHttp.open("GET",url,true);
	xmlHttp.send(null);

	params = "";
	reportError = "";


	var ajax = new Ajax.Updater(
		{success: ''},
		url,
		{method: 'get', parameters: params, onFailure: reportError}
	);

	// var ajax = new Ajax.Updater(
		// {success: ''},
		// url,
		// {method: 'get', parameters: params, onFailure: reportError}
	// );

}	

function getmenuvalue(obj){
 return (obj.options[obj.selectedIndex].value);
}

function formatnumber(n) {
	return Math.round(n*100)/100;
}