Publishing Presence on an Application Endpoint

Hi,

I've created an Application Endpoint which when shown in Communicator shows as offline (even though the application is up and running and users can interact with it).  I would like to publish presence on this endpoint so that it can show to users as "Available" or "Busy".  Think of the concept of a store where it is open between 8 - 4 and closed the rest of the day - so in that scenario, idle is open, offline/busy could be closed.

I understand that on Application Endpoints it is not possible to publish custom state as the endpoints do not support custom grammar strings. 

For publishing Presence I am trying to following this article on MSDN;

http://msdn.microsoft.com/en-us/library/dd280156(office.13).aspx

However after working through the example (and working through some errors on the page) I am still not able to modify the presence of my contact entity as it appears in Communicator which is what I want to see.

Am I missing something in the publishing/subscription of presence of an ApplicationEndpoint in Communicator?

Thanks  - Greg.