Question for a new project

Im working on a new project with gravity reversing as a key component. I'm using NxOgre at the moment, but im not sure its possible to do what I want with it, so I'm just going to ask this on the forums for all the physics wrappers. I need to be able to reverse gravity on one object at a time, but they still need to be able to interact with each other. So my question is basically can I do this with Newton?

Yes, you can.
Gravity works through adding forces in callbacks, you can set the default callback to all bodies, then they will have the same, default gravity. You can also set a custom callback, and then set gravity according to the object that called it. the callback recieves a pointer to the calling object's body (you can store a void* in the body, good for pointers to your object class). you can also set a method of your object class as a callback