How to make an alpha background with DS effect?

[AlexandreJesus]

I need to change my background in postproduction, in photoshop. I rendered the alpha render elements but shows the DS sky, how i make the background black but still receive the nice DS sky and clouds reflection in the windows, door glass? I thought that "Apply to background" will do the trick, disabling don`t showing nothing in the background but appeared the objects scene, but didn`t worrk. The glass stayed all black.


Btw this my first post in here. Continue the good work.

I`m using:
win xp pro sp2
3ds max 9 32 bit
final render stage 1r2.0
Dreamscape 2.5c
Bionatics natfx