I don't have much time right now, but it's easy to make something in lisp without a reactor.
First you need to compose the field format. That can be done with the FIELD-command (see picture)
A lisp file looks something like this (not tested):
;================================================
; AreaDemo using fields 24-05-2006 by J.J.Damstra
; http://www.theswamp.org/index.php?topic=10248.0
;================================================
(defun c:AreaDemo (/ ce entity oba fieldstring)
(vl-load-com)
(setq ce (getvar "CMDECHO"))
(setvar "CMDECHO" 0)
(setq entity (car (entsel "\nSelect a closed polyline: ")))
(setq oba (vla-get-objectid (vlax-ename->vla-object entity)))
;Use the FIELD-command to compose the next line:
;%<\AcObjProp.16.2 Object(%<\_ObjId 2130265440>%).Area \f "%lu2%ps[,m2]%ds44%ct8[1e-006]">%
(setq fieldstring (strcat "%<\\AcObjProp Object(%<\\_ObjId "
(rtos oba 2 0)
">%).Area \f "%lu2%ps[,m2]%ds44%ct8[1e-006]">%"))
; (RE)PLACE THE STRING IN YOUR DRAWING HERE
(setvar "CMDECHO" ce)
(princ)
)