private void gestionarBancoToolStripMenuItem_Click(object sender, EventArgs e)
 {
     if (formBanco == null)
     {
         formBanco             = new FormGestionBanco();
         formBanco.MdiParent   = this;
         formBanco.FormClosed += new FormClosedEventHandler(formBanco_FormClosed);
         formBanco.Show();
     }
     else
     {
         formBanco.Activate();
     }
 }
 void formBanco_FormClosed(object sender, FormClosedEventArgs e)
 {
     formBanco = null;
 }