I need help creating a script for gmax.

What I want is to create my own simpleGeometry, basically a box, that has other propierties, I call it and Actor. This Actor is related to other objects in the scene, so I need a list box where I can add, remove, etc. other objects. My problem is when I try to define the parameters for the main:rollout, and adding, removing, updating..

Also, I managed at some point to add objects, but when I selected a differente objetct, and then selected my Actor again, the list was empty again.

Here's the code:  test.ms