How to rename tabs programmatically on the right click context menu in WinForms TabbedMDIManager?

MyMDITabPanel mtab;
private void tabbedMDIManager_TabControlAdded(object sender, TabbedMDITabControlEventArgs args)
{
   args.TabControl.LabelEdit=true;
   mtab=(MyMDITabPanel)args.TabControl;
}
private void bi_Click(object sender, EventArgs e)
{
   mtab.StartEdit();
}
//Deriving custom TabbedMDIManager for renaming the tabs
public class MyTabbedMDIManager:TabbedMDIManager
{
   protected override MDITabPanel CreateMDITabPanel()
   {
       return new MyMDITabPanel(this);
   }
}
public class MyMDITabPanel:MDITabPanel
{
   public MyMDITabPanel(TabbedMDIManager tmm):base(tmm)
   { }
   public void StartEdit()
   {
       StartLabelEdit();
   }
}

Dim mtab As MyMDITabPanel
Private Sub tabbedMDIManager_TabControlAdded(ByVal sender As Object, ByVal args As TabbedMDITabControlEventArgs)
   args.TabControl.LabelEdit=True
   mtab=CType(args.TabControl, MyMDITabPanel)
End Sub
Private Sub bi_Click(ByVal sender As Object, ByVal e As EventArgs)
   mtab.StartEdit()
End Sub
'Deriving custom TabbedMDIManager for renaming the tabs
Public Class MyTabbedMDIManager
   Inherits TabbedMDIManager
   Protected Overrides Function CreateMDITabPanel() As MDITabPanel
      Return New MyMDITabPanel(Me)
   End Function
End Class
Public Class MyMDITabPanel
   Inherits MDITabPanel
   Public Sub New(ByVal tmm As TabbedMDIManager) : MyBase.New(tmm)
   End Sub
   Public Sub StartEdit()
       StartLabelEdit()
   End Sub
End Class