How to prevent the user from modifying the visibility of a particular toolbar in WinForms Menu(MainFrameBarManager)?

// Will plugin a CustomCommandBarManager
public class CustomMainFrameBarManager : MainFrameBarManager
{
   public CustomMainFrameBarManager(){}
   public CustomMainFrameBarManager(IContainer container, Form form) : base(container, form)
   {  }
   protected override void CreateCommandBarManager()
   {
      if(this.Form != null)
      {
         this.commandBarManager = new CustomCommandBarManager(this.Form, this);
      }
   }
}
//Will exclude a particular toolbar from the toolbar visibility menu.
public class CustomCommandBarManager : CommandBarManager
{
   private ParentBarItem toolbarListItem = null;
   public CustomCommandBarManager(Form form, BarManager manager) : base(form, manager)
   {  }
   // Listen to the Popup event of the ParentBarItem that will contain the toolbar list
   // You will remove unwanted menu items in that event.
   protected override ToolbarListPopupMenu CreateToolbarListPopup()
   {
      ToolbarListPopupMenu popupMenu = base.CreateToolbarListPopup();
      this.toolbarListItem = popupMenu.ParentBarItem;    this.toolbarListItem.Popup += new EventHandler(this.ToolbarList_Popup);  return popupMenu;
   }
   private void ToolbarList_Popup(object sender, EventArgs e)
   {
      ParentBarItem parentItem = sender as ParentBarItem;
      //Remove the BarItem corresponding to the Toolbar that you dont want the user to see
      foreach(BarItem item in parentItem.Items)
      {
         // Looking for the BarName.
         if(item.Text == "Standard") 
         { 
            parentItem.Items.Remove(item); 
            // Note if removing multiple items, use the for loop starting from the bottom of the list.
             break;
         }
      }
   }
}

' Will plugin a CustomCommandBarManager
Public Class CustomMainFrameBarManager Inherits MainFrameBarManager   
    Public Sub New()
    End Sub 'New
    Public Sub New(ByVal container As IContainer, ByVal form As Form) MyBase.New(container, form)
    End Sub 'New
    Protected Overrides Sub CreateCommandBarManager()
       If Not (Me.Form Is Nothing) Then
          Me.commandBarManager = New CustomCommandBarManager(Me.Form, Me)
       End If
    End Sub
End Class
' Will exclude a particular toolbar from the toolbar visibility menu.
Public Class CustomCommandBarManager Inherits CommandBarManager   Private toolbarListItem As ParentBarItem = Nothing
    Public Sub New(ByVal form As Form, ByVal manager As BarManager) MyBase.New(form, manager)
    End Sub 'New
    ' Listen to the Popup event of the ParentBarItem that will contain the toolbar list ' You will remove unwanted menu items in that event.
    Protected Overrides Function CreateToolbarListPopup() As ToolbarListPopupMenu
        Dim popupMenu As ToolbarListPopupMenu = MyBase.CreateToolbarListPopup()
        Me.toolbarListItem = popupMenu.ParentBarItem
        AddHandler Me.toolbarListItem.Popup, AddressOf Me.ToolbarList_Popup
        Return popupMenu
  End Function 'CreateToolbarListPopup
  ' Removing unwanted menu items (corresponding to toolbars) in that event.
  Private Sub ToolbarList_Popup(ByVal sender As Object, ByVal e As EventArgs)
      Dim parentItem As ParentBarItem = CType(sender, ParentBarItem)
      ' Remove the BarItem corresponding to the Toolbar that you don't want the user to see
      Dim item As BarItem
      For Each item In parentItem.Items
          ' Looking for the Bar's BarName.
          If item.Text = "Standard" Then
             parentItem.Items.Remove(item)
             Exit For
         End If
      Next
  End Sub
End Class

// In your Form's constructor, after calling InitializeComponent this.mainFramebarManager1.CustomizationDialog.SetCustomizationPanel(new DerivedCustPanel());