Alan's posted some really nice examples, but here's one that SHOULD catch the possible errors from vla-getboundingbox...
(defun BBox (ent / ll ur)
(if (eq (type ent) 'ENAME)
(if (not (vl-catch-all-error-p
(vl-catch-all-apply
(function vla-getboundingbox)
(list (vlax-ename->vla-object ent) 'll 'ur)
)
)
)
(mapcar (function vlax-safearray->list) (list ll ur))
)
)
)