function floor(number)
{
  return Math.floor(number*Math.pow(10,2))/Math.pow(10,2);
}

function dosum()
{
  // interest rate
  var mi = replaceChars('%','',document.mortgage_calculator.IR.value) / 1200;
  // loan amount
  var la = replaceChars(',','',document.mortgage_calculator.LA.value);la = replaceChars('$','',la);
  // property taxes
  var at = replaceChars(',','',document.mortgage_calculator.AT.value);at = replaceChars('$','',at);
  // Insurance
  var ai = replaceChars(',','',document.mortgage_calculator.AI.value);ai = replaceChars('$','',ai);
  var base = 1;
  var mbase = 1 + mi;
  for (i=0; i<document.mortgage_calculator.YR.value * 12; i++)
  {
    base = base * mbase
  }
  document.mortgage_calculator.PI.value = floor(la * mi / ( 1 - (1/base)))
  document.mortgage_calculator.MT.value = floor(at / 12)
  document.mortgage_calculator.MI.value = floor(ai / 12)
  var dasum = la * mi / ( 1 - (1/base)) +
        at / 12 + 
        ai / 12;
  document.mortgage_calculator.MP.value = floor(dasum);
}


function replaceChars(char_find,char_replace_with,entry)
{
	temp = "" + entry; // temporary holder

	while (temp.indexOf(char_find)>-1)
	{
		pos= temp.indexOf(char_find);
		temp = "" + (temp.substring(0, pos) + char_replace_with + 
		temp.substring((pos + char_find.length), temp.length));
	}
	return temp;
}