Obtaining remote rendering context

This is really a windows issue but since most messages are posted to this topic I thought I woudl risk a cross post.

Does anyone know if it is possible to obtain the rendering contexts that are associated with a window.

I am using a library that handles all the low level OpenGL for my app, but I want to get hold of the pixel information from the screen buffer if possible. I have a handle to the window but not the rendering context.

I know that you aren’t supposed to share rendering contexts between threads but I am only trying to read the data using functionn such as glReadPixels().

I have a screen grab solution that will suffice but I really would like to obtain the depth buffer information.