Receiving status change events in C++?

[Kevin]

We're writing an application that needs to monitor the Messenger status
of multiple users. The application must be written in C++, and it will
run on Windows XP. I've been unable to find an SDK or API to permit
C++ applications to register for and receive contact status change
events.

Has anyone done this? Can you kindly point me in the right direction?
How can a C++ app register to receive Messenger contact status change
events?

Thanks,

Kevin.