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

function dosum()
{
  var mi = document.mortgageCalc.IR.value / 1200;
  var base = 1;
  var mbase = 1 + mi;
  for (i=0; i<document.mortgageCalc.YR.value * 12; i++)
  {
    base = base * mbase
  }
  document.mortgageCalc.PI.value = floor(document.mortgageCalc.LA.value * mi / ( 1 - (1/base)))
  document.mortgageCalc.MT.value = floor(document.mortgageCalc.AT.value / 12)
  document.mortgageCalc.MI.value = floor(document.mortgageCalc.AI.value / 12)
  var dasum = document.mortgageCalc.LA.value * mi / ( 1 - (1/base)) +
        document.mortgageCalc.AT.value / 12 + 
        document.mortgageCalc.AI.value / 12;
  document.mortgageCalc.MP.value = floor(dasum);
  
  var monPrincipal = document.getElementById("monPrincipal");
  var monTax = document.getElementById("monTax");
  var monInsurance = document.getElementById("monInsurance");
  var monTotal = document.getElementById("monTotal");
  
  monPrincipal.innerHTML = formatCurrency(document.mortgageCalc.PI.value);
  monTax.innerHTML = formatCurrency(document.mortgageCalc.MT.value);
  monInsurance.innerHTML = formatCurrency(document.mortgageCalc.MI.value);
  monTotal.innerHTML = formatCurrency(document.mortgageCalc.MP.value); 
}

function formatCurrency(num) {
num = num.toString().replace(/\$|\,/g,'');
if(isNaN(num))
num = "0";
sign = (num == (num = Math.abs(num)));
num = Math.floor(num*100+0.50000000001);
cents = num%100;
num = Math.floor(num/100).toString();
if(cents<10)
cents = "0" + cents;
for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++)
num = num.substring(0,num.length-(4*i+3))+','+
num.substring(num.length-(4*i+3));
return (((sign)?'':'-') + '$' + num + '.' + cents);
}