Different use of bokeh DOF

what i want is maybe hard to explain and maybe its not even possible to do but here it goes.

imagine you have a room with an open doorway. the room I am in is all sharp, but everything behind the doorway is really blury, in DOF.
i dont want to use dof on the camera because i want everything in my room sharp.
so what i want is kind of a DOF material. something like when you use refraction to distort the image when you are looking through a glass material, but instead of refraction it would be distorted with bokeh DOF.
i hope it makes sense.

is there some way how to achieve this effect?