(defun c:BST ( / ss index e obj oldspt oldept newspt newept dist)
   (vl-load-com)
   (prompt "n 양쪽 늘이기 [ bst ]")
   (setq ss (ssget (list (cons 0 "LINE"))))
   (setvar "orthomode" 1) 
   (setq dist (getdist "n ≫ Input the stretch length<or Pick 2point> : "))
   (setq index 0)
   (setq e (ssname ss index))
   (setq obj (vlax-ename->vla-object e))
   (setq oldspt (vlax-get obj 'startpoint))
   (setq oldept (vlax-get obj 'endpoint))  
   (setq newspt (polar oldspt (angle oldept oldspt) dist))
   (setq newept (polar oldept (angle oldspt oldept) dist))
   (vlax-put obj 'startpoint newspt)
   (vlax-put obj 'endpoint newept)
   (setq index (1+ index))
 (princ)
) ; end of defun