(defun c:aa ( / ent obj pts i pt1 ptlst)
  (setq ptlst '())
  (setq ent (car (entsel "\nSelect polyline: ")))
  (if ent
    (progn
      (if (member (cdr (assoc 0 (entget ent))) '("LWPOLYLINE" "POLYLINE"))
        (progn
          (setq obj (vlax-ename->vla-object ent))
          (setq pts (vlax-curve-getEndParam obj))
          (setq i 0)
          (while (<= i pts)
            (setq pt1 (vlax-curve-getPointAtParam obj i))
            (setq ptlst (cons pt1 ptlst))
            (setq i (+ i 1))
          );;while
          (setq ptlst (reverse ptlst))

;; new code
;; new code
          (command "-SECTIONLINES") ;selects the no dialog command
          (command "P") ; points
          (command "") ; section line group
          (command "") ; label style
          (command "") ; prefix
          (command "") ; suffix
          (foreach pt1 ptlst
            (command pt1)
          )
          (command "") ;finish
;; end
;; end

        );; progn - valid polyline
      );; if member
    );; progn - ent selected
    (prompt "\nNothing selected.")
  );; if ent
  (princ)
)