my-util.el

(defun ido-completing-read-multiple (prompt choices &optional predicate require-match initial-input hist def sentinel)
  "Read multiple items with ido-completing-read. Reading stops
  when the user enters SENTINEL. By default, SENTINEL is
  \"_done_\". SENTINEL is disambiguated with clashing completions
  by appending _ to SENTINEL until it becomes unique. So if there
  are multiple values that look like SENTINEL, the one with the
  most _ at the end is the actual sentinel value. See
  documentation for `ido-completing-read' for details on the
  other parameters."
  (let
      ((sentinel (if sentinel sentinel ".done_"))
       (done-reading nil)
       (res ()))

    ;; uniquify the SENTINEL value
    (while (find sentinel choices)
      (setq sentinel (concat sentinel "_")))
    (setq choices (cons sentinel choices))

    ;; read some choices
    (while (not done-reading)
      (setq this-choice (ido-completing-read prompt choices predicate require-match initial-input hist def))
      (if (equal this-choice sentinel)
          (setq done-reading t)
        (setq res (cons this-choice res))))

    ;; return the result
    res
    ))