[Unified Service Desk 2.0] DisableToolbarButton actions

Hello,

Has anyone managed to get the DisableToolbarButton action to work inside the Unified Service Desk?

I have a CRM page hosted control with a toolbar successfully attached. I wish to disable specific buttons inside the toolbar. I can see the Action Call for DisableToolbarButton firing with a value of success returned, however the toolbar button is still enabled. 

I've configured the Action call for disabling the toolbar button as follows:

Hosted Control: <CRM Web Page>

Action: DisableToolbarButton

Data: <Name of toolbar button?

Any ideas?

Les