Here you go.
(defun c:Test (/ int sel ent get)
;;--------------------------------------------;;
;; Author : Tharwat Al Choufi ;;
;; ;;
;; www.AutolispPrograms.WordPress.com ;;
;;--------------------------------------------;;
(and (or (tblsearch "STYLE" "iso")
(entmake '((0 . "STYLE")
(100 . "AcDbSymbolTableRecord")
(100 . "AcDbTextStyleTableRecord")
(2 . "iso")
(70 . 0)
(40 . 0.0)
(41 . 1.0)
(50 . 0.0)
(71 . 0)
(42 . 100.)
(3 . "isocp.shx")
(4 . "")
)
)
)
(or (setq int -1 sel (ssget "_X" '((0 . "TEXT,MTEXT"))))
(alert "No texts found in this drawing.!")
)
(while (setq int (1+ int) ent (ssname sel int))
(and (setq get (entget ent))
(entmod (subst '(7 . "iso") (assoc 7 get) get))
)
)
)
(princ)
)