Is it true a "callback" as "ent',and then replace "notifier-object" by "ent" (vl-load-com) (setq ss (ssget)) (setq en (ssname ss 0)) (setq ent (vlax-ename->vla-object en)) (defun print-radius (notifier-object reactor-object parameter-list) (vl-load-com) (cond ( (vlax-property-available-p notifier-object "Radius" ) (princ "The radius is ") (princ (vla-get-radius notifier-object)) ) ) )