e.commandBar.Parent != null

if (e.commandBar.Controls.Id != 1000 && e.commandBar.Controls.Id != 1001 && e.commandBar.Controls.Id != 1002)

private void CommandBars_Execute(object sender, AxXtremeCommandBars._DCommandBarsEvents_ExecuteEvent e)
{
    switch (e.control.Id)
    {
        ... // All your commandbar execution code goes above here

        default:
            // Activate the selected Window List Form.
            for (int i = 0; i < Workspace.ItemCount; i++)
            {
                if (Workspace.Item(i).Caption == e.control.Caption)
                {
                    Workspace.Item(i).Selected = true;
                    break;
                }
            }
            break;
    }
}

private void CommandBars_InitCommandsPopup(object sender, AxXtremeCommandBars._DCommandBarsEvents_InitCommandsPopupEvent e)
{
    // Build the Window List of Open Mdi Child Forms
    if (!e.commandBar.Parent.IsNull())
    {
        if (e.commandBar.Parent.Caption == "Window")
        {
            // Delete all menu's apart from Cascade, Arrange Horizontally & Arrange Vertically
            for (int i = e.commandBar.Controls.Count; i >= 1; i--)
            {
                if (!e.commandBar.Controls.Id.Includes(1000, 1001, 1002))
                    e.commandBar.Controls.Delete();
            }

            // Get the Active Mdi Child Form
            Form frmActiveForm = this.ActiveMdiChild;

            // Build the Open Window List
            int x = 1;
            foreach (Form frm in this.MdiChildren)
            {
                CommandBarControl ctrl = e.commandBar.Controls.Add(XTPControlType.xtpControlButton, x, frm.Text.Trim());
                ctrl.BeginGroup = (x == 1 ? true : false);
                ctrl.Checked = (frmActiveForm.Text == ctrl.Caption ? true : false);
                x++;
            }
        }
    }
}