Elisp newbie trying a derived mode

[davex]

Hello all, my first post here, and I've recently started coding elisp.
I want a simple method of interactively selecting multiple files or
directories, and passing the selection list to an external program.
My first thought was to tweak dired mode, so that I could just navigate
around dirs, marking files and dirs that I want (with 'm') and then
have a special key call dired-do-shell-command with something to
append each marked entry to a text file.

Question: is there something simpler than dired to tweak? All I really
need is the directory navigation and marking capability.

Another question: as long as I run dired first, the following code lets
me do M-x file-select-mode, showing a dired type buffer, and my
C-c k *does* print the message (yippee), but when I try to mark a
file with 'm', I get 'No subdir-alist in elisp'. Anyone know why?

(defun !fsm-keyfunc ()
  (interactive)
  (message "you pushed the key")
)
(defun !fsm-func ()
  (local-set-key "\C-ck" '!fsm-keyfunc)
)
(define-derived-mode file-select-mode
  dired-mode "file-select"
  "Major mode for file selection."
  (setq file-select-mode-hook '!fsm-func)
)

Thank you for your time! Any guidance will be greatly appreciated.