先获取点坐标，然后进行排序，赋值。

(defun c:test()
(princ "\n请选取矩形:")
(if (setq ssa (ssget ":S" '((0 . "LWPOLYLINE") (90 . 4))))
(progn
(setq dxf (entget (ssname ssa 0)))
(setq dxf70 (cdr (assoc 70 dxf)))
(setq pts (mapcar 'cdr (vl-remove-if '(lambda(x)(/= (car x) 10)) dxf)))
(if (= (logand 1 dxf70) 1)
(progn
(setq s1 (apply 'mapcar (cons 'min pts)))
(setq s3 (apply 'mapcar (cons 'max pts)))
(setq s2 (list (car s2) (cadr s3)))
(setq s4 (list (car s3) (cadr s2)))
)
)
)
)
(princ)
)