updating buffer window while accepting minibuffer input

["Buchs, Kevin J." <buchs.kevin@mayo.edu>]

This is a follow-up to "regexp nirvana - near miss" (thanks Drew for 
giving me this programming burden ;-). I'm wanting to traverse a list of 
buffer positions according to minibuffer keystrokes and have the 
referenced buffer position update (and eventually highlight) much like 
isearch-*. I'm stuck on the buffer position not actually updating 
whilest I am in the midst of (read-minibuffer-input). I have spent about 
two hours delving into how isearch works and came out without a clue as 
to how it actually gets minibuffer reading activated. So, I'm seeking 
help. Code follows signature.

Kevin Buchs   Research Computer Services   Phone: 507-538-5459
Mayo Clinic   200 1st. St SW   Rochester, MN 55905
http://mayoclinic.org  http://facebook.com/MayoClinic  http://youtube.com/MayoClinic  http://twitter.com/MayoClinic

(defun regexpneg-fwd ()
    (interactive)
      ;; Move to next match
      (if (< regexpneg-pointer (1- (length regexpneg-list)))
             (progn
                  (set-buffer regexpneg-buffer)
                  (setq regexpneg-pointer (1+ regexpneg-pointer))
                  (goto-char (nth regexpneg-pointer regexpneg-list))
                  (recenter 5)
                  (message "buffer: %S, position: %d, pointer: %d"
                         (current-buffer) (point) regexpneg-pointer))))


(defun regexpneg-rev ()
    (interactive)
      ;; Move to prior match
      (unless (= regexpneg-pointer 0)
             (set-buffer regexpneg-buffer)
             (setq regexpneg-pointer (1- regexpneg-pointer))
             (goto-char (nth regexpneg-pointer regexpneg-list))
             (recenter 5)
             (message "buffer: %S, position: %d, pointer: %d"
                  (current-buffer) (point) regexpneg-pointer)))


(defun regexpneg (part negpart)
      "Search for regexp part, not followed by regexp negpart; You can 
advance in search hits with C-s or SPACE. Reverse with C-r or DEL"
      (interactive)
      (let (
                      (point-start (point))
                      (subsetnotlist '()))

             ;; Save a reference to current buffer
             (setq regexpneg-buffer (current-buffer))

             ;; Search for 'part' - return list of locations = 
regexpneg-list
             (setq regexpneg-list '())
             (while (re-search-forward part nil t)
                  (setq regexpneg-list (append regexpneg-list
  (list (match-beginning 0)))))

             ;; Search for 'part'+'negpart' - return list of locations = 
subsetnotlist
             (goto-char point-start)
             (while (re-search-forward (concat part negpart) nil t)
                  (setq subsetnotlist (append subsetnotlist (list 
(match-beginning 0)))))

             ;; Delete members of subsetnotlist from regexpneg-list
             (dolist (var subsetnotlist)
                  (delq var regexpneg-list))

             ;; Check for keymap or create it
             (unless (keymapp 'regexpneg-keymap)
                  (setq regexpneg-keymap (make-sparse-keymap))
                  (define-key regexpneg-keymap "\C-s" 'regexpneg-fwd)
                  (define-key regexpneg-keymap " " 'regexpneg-fwd)
                  (define-key regexpneg-keymap "\C-r" 'regexpneg-rev)
                  (define-key regexpneg-keymap "DEL" 'regexpneg-rev)
                  (define-key regexpneg-keymap "\C-j" 'exit-minibuffer)
                  (define-key regexpneg-keymap "\C-m" 'exit-minibuffer))

             ;; Set index-pointer
             (setq regexpneg-pointer 0)

             ;; Move to first match
             (goto-char (nth regexpneg-pointer regexpneg-list))
             (message "buffer: %S, position: %d, pointer: %d"
                  (current-buffer) (point) regexpneg-pointer)

             ;; Show minibuffer for further options
             (setq resp (read-from-minibuffer
                  "REN: fwd=C-s,SPACE; rev=C-r,DEL; exit=C-j,C-m: " nil
                  regexpneg-keymap))
             (message "got response '%s'" resp)))