Unseen by camera? - Cutaway image help

[stretch]

Ok Guys, Ive got a problem.... and a deadline

Trying to produce a cutaway image of a bathroom but am getting a problem with the objects that are unseen by camera - and how they affect a mirror/reflected surface.
hopefully that made some sense.

I have tryed this with rc1 and lw9.6

below lists my object and surfaces if that helps
the scene contains 3 objects.

the objects in the scene--
-the room
-the wall that's cutaway - this has unseen by camera ticked on.
-and the background

the surfaces - there are only 3 in this scene
-the mirror
-the background
-and all the rest

none of these surfaces are double sided.

[Janusz Biela]

This is no work

G. know abount total exclude obiect from scene - but I don`t received this shader yet!
Unseen by camera hide Your obiect but not hide in reflections.....