[vtkusers] adding a custom event in Windows

[Maurizio Turatti]

I have a Motif vtk C++ app which checks a socket and calls a custom function if
there's a write event on it. This is done with XtAppAddInput. How can I do
something similar in Windows? I want to set my callbacks, and the
vtkInteractorStyleUser allows me only to deal with the mouse, if I well
understand.

Thanks,
Maurizio