Mouse position inside view

So. OpenGl has rendered my image in 3D.
Now I want to know where my mouse is when
it floats over the view.
(i.e. the line projection from
the mouse through my picture)

Does OpenGL provide any transform at
all for helping me determine this?

Thanks for any suggestions!

try gluUnProject()

does the job, its quite fiddly though, so be prepared for some headaches