function button_label_update(new_lable)
{
	var button_calc = document.getElementById('button_calc');
	button_calc.value = new_lable;
}
function update_amount_down()
{
	var total = document.getElementById('home_price');
	var amount_down = document.getElementById('amount_down');
	var percent_down = document.getElementById('percent_down');
	var amount_down_tmp = total.value * percent_down.value / 100;
	amount_down.value = amount_down_tmp.toFixed(0);
	return;
}
function update_percent_down()
{
	var total = document.getElementById('home_price');
	var amount_down = document.getElementById('amount_down');
	var percent_down = document.getElementById('percent_down');
	var percent_down_tmp = amount_down.value / total.value * 100;
	percent_down.value = percent_down_tmp.toFixed(2);
	return;
}
function dosum()
{
  //var mi = document.temps.IR.value / 1200;
  var home_price = document.getElementById('home_price');
  var amount_down = document.getElementById('amount_down');
  var percent_down = document.getElementById('percent_down');
  var years = document.getElementById('years');
  var interest = document.getElementById('interest');
  var mortgate_payment = document.getElementById('mortgage_payment');
  
  //computed results:
  var amount_financed = home_price.value - amount_down.value;
  var monthly_interest = interest.value / (12 * 100);
  var num_months = years.value * 12;
  var mortgage_payment = amount_financed*(monthly_interest/(1-(Math.pow(1+monthly_interest,(-1 * num_months)))));

  //display output
  document.getElementById('out_amount_down').innerHTML = '$' + parseFloat(amount_down.value).toFixed(2);
  document.getElementById('out_amount_financed').innerHTML = '$' + amount_financed.toFixed(2);
  document.getElementById('out_mortgage_payment').innerHTML = '$' + mortgage_payment.toFixed(2);
}