<!--

 // validation function

function isValid(entry, a, b) {

  if (isNaN(entry.value) || (entry.value==null) || (entry.value=="") || (entry.value < a) || (entry.value > b)) {

  alert("Invalid entry. Enter a number between " + a + " and " + b + ".")

	entry.focus()

  entry.select()

	return false

  }

	return true

}


// clear results fields when input values changed

function clearCalcs(form) {

	form.num_months.value = ""

	form.total_pay.value = ""

	form.total_int.value = ""

}


function calculate(form) {

// send entries to validation function

// exit if not valid

	if (!isValid(form.balance, 0, 100000)) {  

		return false

	} else if (!isValid(form.interest, 0, 30)) {  

		return false

	} else {         

		var init_bal = eval(form.balance.value);

	}

	if (!isValid(form.mnth_pay, init_bal*.02, init_bal)) {

		return false

  } else {

	// variables used in calculation

	var cur_bal = init_bal;		// used in loop

	var interest = eval(form.interest.value/100);

	var mnth_pay = eval(form.mnth_pay.value);

	var fin_chg = 0;			// finance charge

	var num_mnths = 0;

	var tot_int = 0;

  }

	
  while (cur_bal > 0) {

    fin_chg = cur_bal*interest/12;

    cur_bal = cur_bal - mnth_pay + fin_chg;

    num_mnths++;

			if (num_mnths > 75) {

      	alert("We are interrupting this process to prevent a hang which may result with a very high balance, high interest rate and low monthly payment.\n\nTry entering a higher monthly payment amount." )

				form.mnth_pay.focus()

				form.mnth_pay.select()

				return

      }

    tot_int += fin_chg;

  }

	
// display result

	form.num_months.value = num_mnths;

	form.total_pay.value ="$" + round(init_bal + tot_int);

	form.total_int.value ="$" + round(tot_int);

   }


// round to 2 decimal places

function round(x) {

	return Math.round(x*100)/100;

}

// -->