vfx shot texture mapping

[particletree]

I worked out the mapping, I use mapping from surface "continuously" and when the briks start moving as "on event entry" in the next event.

1. one problem, the moving bricks only take one colour sample from the surface when I use mapping from object, so the Bricks end up having one colour only rather than a texture from the surface applied to the. how can I fix that?

2. is it possible to apply a different material to a different event. I only see the Multi/sub-object as option with different IDs for different event, is there no other way to apply different material to different events?

thanks