I’m using the grayscale effect included in the pro package. Now I’m wondering if its possible to use the effect on a few objects only?
Has anyone of you done this before or could tell me how this could be accomplished?
I don’t have pro, but in theory, you could create two cameras, and parent one to the other. The cameras would share rotation, rotation, and far clip pane. After that, you would set one to view all layers other than the “Selected” layer. And then, you could set the other camera to only see the “Selected” layer. Next, apply the grayscale script to the camera that can only see the “Selected” layer. Finally, move all selected objects to the “Selected” layer.
Oh, and two more things:
Make the camera that only sees the “Selected” layer, render above the one that doesn’t see the “Selected layer”. (By increasing depth). Then, set “Clear Flags” to none in the camera that sees the “Selected” layer.
Perfect!
That did the job 
thank you.