APM variable assign examples

I was wondering if it is away to have VMware View client when is configured via the APM to read only logon.last.logonname. When you authenticate using the view client, you get two windows one for (Radius) and the second one for (Active Directory); the issue is that when you get the AD window, the username is not in realy mode and you can change the username. Does anyone knows how to get custom variable to force it to read only? I am not talking about the Webtop... this is only with Horizon Client View...