Событие ReadOnlyChanged в TextBox Одно для нескольких TextBox-ов

TB_total_sale.ReadOnlyChanged += new EventHandler(TB_total_sale_ReadOnlyChanged);
TB_prepayment.ReadOnlyChanged += new EventHandler(TB_prepayment_ReadOnlyChanged);

        private void TB_total_sale_ReadOnlyChanged(object sender, EventArgs e)
        {            
            if (TB_total_sale.ReadOnly == true) {TB_total_sale.BackColor = SystemColors.Control;}
            else {TB_total_sale.BackColor = Color.PaleGreen;}
        }
 
        private void TB_prepayment_ReadOnlyChanged(object sender, EventArgs e)
        {
            if (TB_prepayment.ReadOnly == true) { TB_prepayment.BackColor = SystemColors.Control; }
            else { TB_prepayment.BackColor = Color.PaleGreen; }
        }

TB_total_sale.ReadOnlyChanged += new EventHandler(TB_total_sale_ReadOnlyChanged);
TB_prepayment.ReadOnlyChanged += new EventHandler(TB_total_sale_ReadOnlyChanged);