Calling managed code from unmanaged code

Hi,

I have a situation where I need to write a global hook. I have to
write the hook in a C++ dll since .net does not support implementation
of global hooks. But I want to use this hook from a .net application.
So far so good. But I also want my hook to call a function in my .net
application (the one that initiates the hook). How would I go about
doing this?