Updating an ActiveX Property with vlax-put-property
Using the Visual LISP Environment
Attaching Reactors to AutoCAD Drawings
You can use reactors for event notification.
Visual LISP® not only makes program development easier and faster, it also provides new functionality to LISP applications. For example, you can attach reactors to entities in the AutoCAD® drawing window, allowing your application to respond to user actions on these entities.