Changing the Sign In state of an agent in an agent group

I have been advised to repost the question in this specific forum, as it is considered more relevant to the nature of my query....

We have developed a client which runs against the Lync Client with UI Suppression turned on. 

However we need to add some additional functionality which does not seem to be available from the Lync Client SDK, I have posted something similar on that forum already without success, so I am seeking information on how I can implement this functionality via another Lync interface.

The user of our application answers calls which are fed to it from Queues/Workflows configured with the user as a group agent.

What we need to be able to do is allow the user to sign in or out of individual queues/agent groups from our user interface such that they can control which queues feed calls to them.  I realise that this functionality is available as a Web UI under Lync

(https://<web_pool FQDN>/RgsClients/Tab.aspx.)

but we need to have all this functionality such that it coheres within a single application.

I would be grateful for suggestions on how to do this.  So far I have considered

- acting as a http client and posting the checkbox page which signs the agent in or out of individual queues.  This is a non starter because the web page controls are dynamically created and named via aspx and viewstates.  Also this uses https which makes things more awkward.

- toggling the [rgsdyn].[dbo]. [AgentGroupSignInStates] state in the database.  This gets changed when a checkbox is toggled, but setting this on directly from our client for an agent/queue does not enable queued calls to be offered to that agent.

Can anybody suggest which interface I should be using to programmatically sign agents in or out of a given agent group.
This is an important requirement for us.  Any suggestions or workarounds gratefully accepted.

Thanks