private void btnAgregarMascota_Click(object sender, EventArgs e)
        {
            Cliente cli = new Cliente();

            if (dgbAgregarCliente.RowCount == 0)
            {
                MessageBox.Show("No hay clientes cargados", "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                cli = (Cliente)dgbAgregarCliente.CurrentRow.DataBoundItem;

                if (mascota == null)
                {
                    mascota             = new frmAgregarMascota(cli);
                    mascota.MdiParent   = this.MdiParent;
                    mascota.FormClosed += new FormClosedEventHandler(MascotaFormClosed);
                    mascota.Show();
                }
            }
        }
 void MascotaFormClosed(object sender, EventArgs e)
 {
     mascota = null;
 }