private void txtCodigo_KeyPress(object sender, KeyPressEventArgs e)
        {
            var a = new MyLibrary.Validacion();

            a.ValidaNumero(e);

            if (e.KeyChar == 13)
            {
                txtCantidadEx.Focus();
            }
        }
        private void txtCantidadEx_KeyPress(object sender, KeyPressEventArgs e)
        {
            var a = new MyLibrary.Validacion();

            a.ValidaNumero(e);
        }