protected void LoanDur_SelectedIndexChanged(object sender, EventArgs e)
        {
            var pressedButton = sender as RadioButtonList;
            var selected      = pressedButton.SelectedItem;

            if (selected.Value == "Other")
            {
                otherBox.Enabled = true;
                otherBox.Focus();
            }
            else
            {
                otherBox.Enabled = false;
                otherBox.Text    = String.Empty;
                Princ.Focus();
            }
        }
        protected void submit_Click(object sender, EventArgs e)
        {
            string principal     = "" + Princ.Text + "";
            string duration      = "" + LoanDur.Text + "";
            string rate          = "" + InterestRate.Text + "";
            string otherDuration = "" + otherBox.Text + "";

            // use the function to calculate the monthly payment
            string output = MortgageHelper.ValidateMortgage(principal, duration, rate, otherDuration);

            result.Text = output;

            //IDataHelper io = new IOHelper();
            IDataHelper io = new IOHelper_Database();

            io.WriteMortgage(output);

            Princ.Focus();
        }