(defun c:atx (/ sg) (vl-load-com)
  (if (and (setq ad (vla-get-activedocument (vlax-get-acad-object))
                 st (getstring T "\nEnter text:")
                 sg (ssget (list (cons 0 "*text")))))
    (progn
      (vla-startundomark ad)
      (repeat (setq n (sslength sg))
        (setq ob (vlax-ename->vla-object (ssname sg (setq n (1- n)))))
        (vla-put-TextString ob (strcat st (vla-get-TextString ob))))
      (vla-endundomark ad)
    )
  ) (princ)
)