private void gestionEmpleadoToolStripMenuItem_Click(object sender, EventArgs e)
 {
     if (formEmpleado == null)
     {
         formEmpleado             = new FormGestionEmpleado();
         formEmpleado.MdiParent   = this;
         formEmpleado.FormClosed += new FormClosedEventHandler(formEmpleado_FormClosed);
         formEmpleado.Show();
     }
     else
     {
         formEmpleado.Activate();
     }
 }
 void formEmpleado_FormClosed(object sender, FormClosedEventArgs e)
 {
     formEmpleado = null;
 }