private void gestionCargoToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (formCargo == null)
            {
                formCargo             = new FormGestionCargo();
                formCargo.MdiParent   = this;
                formCargo.FormClosed += new FormClosedEventHandler(formCargo_FormClosed);

                formCargo.Show();
            }
            else
            {
                formCargo.Activate();
            }
        }
 private void formCargo_FormClosed(object sender, FormClosedEventArgs e)
 {
     formCargo = null;
 }