how to set local key in dired to use vm on file

[Gilbert Harman]

Could anyone advise me how to use (set-local-key) or something else so that
when I am in dired and the cursor is over a file, I get vm-visit-folder to
visit that file?

I can get as far as:

(setq dired-mode-hook
      '(lambda ()
     (local-set-key "V" 'vm-visit-folder)))

But that still prompts me for the name of the file to visit.

Thanks in advance.

 Gil