посмотри скрипт SubLink здесь:
http://dg.cgnation.com/scripts.htm
или используй:
Attachment Constraint
Animation menu > Constraints > Attachment Constraint
The Attachment constraint is a Position constraint that attaches an object's position to a face on another object (the target object doesn't have to be a mesh, but must be able to convert itself to a mesh).
By keying different attachments over time, you can animate the position of an object over the irregular surface of another object, even if that surface is changing over time.
удачи