How can we access to the sip account of Office Communicator in ASP .NET c#

Hi,

I am working on a client side web application of Live Communications Server 2005 using ASP .NET 2.0 with C#. In office communicator 2005, I added a button which links to aspx web page of the application. In this aspx page I need to get the identity (or sip-account or email address) of the user who logged in office communicator (NOT the one who logged in the Windows operating system). Right now my program is working with the current user which logged on to the windows OS. Please help me about this problem. Any suggestion would be really appreciated.