[Closed] dynamic scripting..need a hint

Hi all, regarding a tool like the “spacing tool,” what is the underlying MAXscript principle going on here? (For example, how you can dynamically change the number of items on the spline). Do I need to use expressing/script controllers? Or is it putting custom attributes on the instances and then deleting them when you change the number? Any help is much appreciated, as I am trying to write a similar tool.