Ok so far the I have 2 objects, one a passive RB, one a active RB that has an expression on its impulse to make it move in the Z direction.

Below is an expression that makes there colour change when getting with in a certain proximity of each other...

//get objects translates
vector $obj1=`getAttr obj1.translate`;
vector $obj2=`getAttr obj2.translate`;

//subtract one from other
float $mag = mag($obj2-$obj1);

//change colour when within certain proximity
if ($mag <= 10)
setAttr lambert1.color 1 .5 .5;
else
setAttr lambert1.color .5 .5 1;

This is showing it recognises the proximity, now how would I go about making the active RB go round the passive RB?

Thanks

Chris