(defvar *code*)

(defun calling-by-two-funcs ()
  (= 200 *code*))

(defmacro defmagicfun (name (&rest arguments) &body body)
  `(defun ,name ,arguments
     (when (funcall #'calling-by-two-funcs)
       ,@body)))

(defmagicfun show-1 ()
  1)

(defmagicfun show-2 ()
  2)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

CL-USER> (let ((*code* 200))
           (show-1))
1

CL-USER> (let ((*code* 200))
           (show-2))
2

CL-USER> (let ((*code* 404))
           (show-1))
NIL

CL-USER> (let ((*code* 404))
           (show-2))
NIL