Custom gina.dll for advanced remote desktop function

I have a pc with enabled Remote Desktop and work on this pc as
If another pc connect to this pc as Administrator my session will be
disconnected and the other user can work with my session. I'm
searching for a
way that I can confirm or deny this adoption first.
I found no way to do this with standard windows so I decided to write
custom gina.dll

I take the ginastub from plattform SDK and try to modify it.
And now there's the problem, i dont't know where to write my code. My
Idee is that if gina.dll detects a remote connect that want to adopt
my session, it displays a messagebox in the console session which asks
the user if the adoption is ok or not.

Does anyone know where i have to write the code for my messagebox?