private void toolEstadistica_Click(object sender, EventArgs e)
 {
     if (forEstadistica == null)
     {
         forEstadistica             = new FrmEstadistica();
         forEstadistica.MdiParent   = this;
         forEstadistica.FormClosed += new FormClosedEventHandler(CerrarForma5);
         forEstadistica.Show();
     }
     else
     {
         forEstadistica.Activate();
     }
 }
 void CerrarForma5(object sender, FormClosedEventArgs e)
 {
     forEstadistica = null;
 }