<!-- // From TexasTrader.com  01/29/2004
function checkNumber(input, min, max, msg) {
  msg = msg + " field has invalid data: " + input.value;
  var str = input.value;
  for (var i = 0; i < str.length; i++) {
    var ch = str.substring(i, i + 1)
    if ((ch < "0" || "9" < ch) && ch != '.') {
      alert(msg);
      return false;
    }
  }
  var num = parseFloat(str)
  if (num < min || max < num) {
    alert(msg + " not in range [" + min + ".." + max + "]");
    return false;
  }
  input.value = str;
  return true;
}

function computeField(input) {
  if (input.value != null && input.value.length != 0)
  if (checkNumber(input,.001,10000000,input.title)) {
    input.value = "" + eval(input.value);
    computeForm(input.form);
  }
}

function computeForm(form) {
  if ((form.payments.value == null || form.payments.value.length == 0) ||
      (form.interest.value == null || form.interest.value.length == 0) ||
      (form.principal.value == null || form.principal.value.length == 0)) {
    return;
  }
  if (!checkNumber(form.payments, 1, 480, "# of payments") ||
    !checkNumber(form.interest, .001, 99, "Interest") ||
    !checkNumber(form.principal, 100, 10000000, "Principal")) {
    form.payment.value = "Invalid";
    return;
  }
  var i = form.interest.value;
  if (i > 1.0) {
    i = i / 100.0;
    form.interest.value = i;
  }
  i /= 12;
  var pow = 1;
  for (var j = 0; j < form.payments.value; j++)
    pow = pow * (1 + i);
    money = "" + .01* Math.round(100*(form.principal.value * pow * i) / (pow - 1));
    dec = money.indexOf(".");
    dollars = money.substring(0,dec); 
    cents = money.substring(dec+1,dec+3);
    cents = (cents.length < 2) ? cents + "0" : cents;
    money = dollars + "." + cents;
    form.payment.value = money;
}

function clearForm(form) {
  form.payments.value = "";
  form.interest.value = "";
  form.principal.value = "";
}
// -->