function MM_preloadImages() { //v3.0
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}

function MM_swapImgRestore() { //v3.0
  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}

function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImage() { //v3.0
  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
   if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}

function newwin(URL,name,features)
{
window.open(URL,name,features);
}
function mapwin(URL,name)
{
window.open(URL,name,'width=524,height=345,top=40,left=200,scrollbars=no,toolbar=no,resizable=no,hotkeys=no');
}

function formatNumber(val,digits,minval,maxval)
{
	var sval = "" + numval(val,digits,minval,maxval);
	var i;
	var iDecpt = sval.indexOf(".");
	if (iDecpt < 0) iDecpt = sval.length;
	if (digits != null && digits > 0)
	{
		if (iDecpt == sval.length)
			sval = sval + ".";
		var places = sval.length - sval.indexOf(".") - 1;
		for (i = 0; i < digits - places; i++)
			sval = sval + "0";
	}
	var firstNumchar = 0;
	if (sval.charAt(0) == "-") firstNumchar = 1;
	for (i = iDecpt - 3; i > firstNumchar; i-= 3)
		sval = sval.substring(0, i) + "," + sval.substring(i);

	return sval;
}

function filterChars(s, charList)
{
	var s1 = "" + s; // force s1 to be a string data type
	var i;
	for (i = 0; i < s1.length; )
	{
		if (charList.indexOf(s1.charAt(i)) < 0)
			s1 = s1.substring(0,i) + s1.substring(i+1, s1.length);
		else
			i++;
	}
	return s1;
}

function makeNumeric(s)
{
	return filterChars(s, "1234567890.-");
}
function numval(val,digits,minval,maxval)
{
	val = makeNumeric(val);
	if (val == "" || isNaN(val)) val = 0;
	val = parseFloat(val);
	if (digits != null)
	{
		var dec = Math.pow(10,digits);
		val = (Math.round(val * dec))/dec;
	}
	if (minval != null && val < minval) val = minval;
	if (maxval != null && val > maxval) val = maxval;
	return parseFloat(val);
}

function geomSeries(z,m,n)
{
	var amt;
	if (z == 1.0) amt = n + 1;
	else amt = (Math.pow(z,n + 1) - 1)/(z - 1);
	if (m >= 1) amt -= geomSeries(z,0,m-1);
	return amt;
}

function futureValue(p,r,y)
{
	return p*Math.pow(1+r,y);
}

function mortgagePayment(p,r,y)
{
	return futureValue(p,r,y)/geomSeries(1+r,0,y-1);
}

function doCalc()
{
	var r = numval(document.mainform.Interest.value)/100;
	var p = numval(document.mainform.Price.value);
	var y = numval(document.mainform.Years.value);

	document.mainform.Mortgage.value = formatNumber(mortgagePayment(p,r/12,y*12),2);
}