private void buttonAdd_Click(object sender, EventArgs e)
        {
            DlgSessionVariable        dlg = new DlgSessionVariable();
            SessionVariableCollection ow  = new SessionVariableCollection(_owner.Owner);

            for (int i = 0; i < listBox1.Items.Count; i++)
            {
                ow.Add(listBox1.Items[i] as SessionVariable);
            }
            dlg.LoadData(ow, null);
            if (dlg.ShowDialog(this) == System.Windows.Forms.DialogResult.OK)
            {
                listBox1.Items.Add(dlg.Return);
            }
        }