function floor(number)
{
  return Math.floor(number*Math.pow(10,2))/Math.pow(10,2);
}
function calculateIt(formtoCheck) {
var payment;
  var mi = formtoCheck.credit.value / 1200;
  var base = 1;
  var mbase = 1 + mi;
  for (i=0; i<48; i++)
  {
    base = base * mbase;
  }

  payment = floor(formtoCheck.amount.value * mi / ( 1 - (1/base)));

document.form1.payment.value ='$' + payment;
return false;
}//calculateIt