This is a cool routine to update the revision field...
;;;;
;;;;Beginning of the AutoLISP routine
;;;
(defun add-record (/ Xrec Xname)
(setq Xrec '((0 . "XRECORD"

(100 . "AcDbXrecord"

(1 . "DWGPROPS COOKIE"

(9 . ""

)
)
(setq Xname (entmakex Xrec))
(dictadd (namedobjdict) "DWGPROPS" Xname)
)
(prompt "\nType in UPDREV to start this routine"

(defun c:updRev (/ xlist rev)
(setq Rev (getstring "\nEnter drawing Revision Number: "

)
(setq xlist (dictsearch (namedobjdict) "DWGPROPS"

)
(if Xlist
(progn
(dictremove (namedobjdict) "DWGPROPS"

(dictadd (namedobjdict) "DWGPROPS" (entmakex (subst (cons 9 Rev)
(assoc 9 xlist) xlist)))
)
(progn
(add-record)
(setq xlist (dictsearch (namedobjdict) "DWGPROPS"

)
(dictremove (namedobjdict) "DWGPROPS"

(dictadd (namedobjdict) "DWGPROPS" (entmakex (subst (cons 9 Rev)(assoc
9 xlist) xlist)))
;(entmod (subst (cons 9 Rev) (assoc 9 xlist) xlist))
)
)
(princ)
)
;;;;
;;;;End of the AutoLISP routine
;;;
"Whether you think that you can, or that you can't, you are usually right "
.. Henry Ford