XPresso help....multiple object axis?

Hey I'm trying to create something using xpresso and I'm getting stuck. It comes down to 2 different parts:

Part 1:
Basically I have a group of objects that all need to rotate around a fixed point, a null object. I want to drive the rotation using xpresso. These objects aren't rotating around their own separate object axis, but rather the object axis of my null object. They need to move together like they were grouped...

Part 2: BECAUSE I can't just group them together, because some objects need to belong to multiple groups. The next part of my goal is to have another different object axis that the same objects could rotate around.

I'm thinking there is a way to do this in xpresso. Anybody have any idea on part 1 or part 2. Any help would be appreciated.