real quick.......
(if (setq ent (car (entsel)))
(progn
(setq obj (vlax-ename->vla-object ent))
(if (vlax-property-available-p obj 'Arrowhead1Type T)
(vlax-put-property obj 'Arrowhead1Type acArrowArchTick)
)
(if (vlax-property-available-p obj 'Arrowhead2Type T)
(vlax-put-property obj 'Arrowhead2Type acArrowArchTick)
)
)
)
(vlax-release-object obj)