I want to prevent other users to change my drawinginformation, so I freeze my layers. On the other hand they must be able to add their own Acad entities in this same drawing. I have a drawing with all layers frozen in AutoCAD 2002 Is it possible to trigger on the event "unfreeze layer" , so I can execute some program code? Notice that the user also can unfreeze layers in the ACAD toolbar. I cannot find out how to trigger this event consequently. If this is not posible how can I prevent other users to edit my drawing. Notice it must be possible for the users to add drawing information in other layers. Thanks for your hellp