How to create a pass-through window with its top at the ceiling?

[4ndrew]

I realize that I could probably do this with three separate walls or something, but would like to do it in a single (window pass-through) step if possible..

 

How can I open this gap so that the opening goes all the way to the ceiling?  (green line)

 

thanks

 

 

[Rookie65]

Have you thought of setting the top of the window at the rough ceiling height? If you're worried about casing showing, put a very small lintel on the window