Binding Keymap prefix to Major Mode

[Tim Johnson <tim@johnsons-web.com>]

Hi:
I've been working on a major mode for the rebol programming language.
The following code has been evaluated:
(defvar rebol-keymap (make-sparse-keymap) "Rebol mode keymap")
(defcustom rebol-keymap-prefix [(control ?')]
   "*Keymap prefix string for rebol-keymap"
   :type 'string
   :group 'rebol)
(local-set-key rebol-keymap-prefix rebol-keymap)
(define-key rebol-keymap "b" 'previous-rebol-definition)
;; When I load a file that auto-loads the mode, I find
;; that "b" is bound to 'previous-rebol-definition, not
;; to "\C-' b" which is what I hope for.
NOTE: I've tried [(control \')] and [(control c)(control c)]
as prefix symbols with the same (lack of) results.
I presume that something else needs to be done to properly bind
this prefix to the keymap.

All help, docs and examples are welcome.

TIA
Tim