MDI tabs -- how to turn off?

The documentation for CommandBars says that the MDI Tabbed interface can "easily be turned on and off via code".  I can turn it on, but how do I turn it off?

<later> Here is more information.

Using the ActiveX Sample RibbonMDISample, I can see that
    CommandBars.ShowTabWorkspace (True/False)
does work perfectly. No problem here. This turns TabWorkspace on or off.

But using ActiveX Sample  GUISample
when I add the line CommandBars.ShowTabWorkspace (False) it does not have any effect. The TabWorkSpace is always shown.

And in my own application, ShowTabWorkspace (False) does not work. I cannot turn off the TabWorkspace.

I guess there is something that is overruling the TabWorkspace False.

Any ideas what is causing this??

Thank you for the reply.

But please check my original message. I added note that ShowTabWorkspace False does work OK in the RibbonMDISample, but does NOT work in other samples, or in my own application.

There must be something else that is preventing the ShowTabWorkspace  false from working.  For example, I think the RibbonMDISample does not use Docking Manager, but my app with Docking Manager does include Docking.

Any more ideas please what stops ShowTabWorkspace False from working?