private void rbResidential_CheckedChanged(object sender, EventArgs e)
        {
            // When Residential radio button is checked
            // We disable the second KWH entry box and ask the user to enter regular KWH

            // Change the labels
            lblKWH1.Text = "Enter kWh Used:";
            lblKWH2.Text = "";

            // Clear the two KWH entry boxes
            txtKWH1.Text = "";
            txtKWH2.Text = "";

            // Set the tags for the KWH entry boxes
            txtKWH1.Tag = "Enter kWh Used";
            txtKWH2.Tag = "";

            // Enable the first entry box, but disable the second one
            txtKWH1.ReadOnly = false;
            txtKWH2.ReadOnly = true;

            // Provide the Residential description in the rich text box
            rtbCustDesc.Text = Residential.CustomerDescription();
        }