[Orgmode] Can this function be written better?

[Nathan Neff]

I'd like to be able to easily toggle the showing/hiding of CLOSED clock
items in the agenda.

I have a function that does exactly that.  My Lisp is terrible (I bet that's
never been said before :-) and I want to try to improve it.

Any suggestions how to improve/refactor the following function?

(defun njn/agenda-toggle-show-closed()
  "Toggle whether closed clock thingies are shown in the agenda"
  (interactive)
  (if (eq njn/org-agenda-show-closed 't)
      (progn (setq org-agenda-log-mode-items (quote (clock)))
             (setq njn/org-agenda-show-closed nil)
             (message "NOT Showing closed clock entries in agenda"))
    (progn (setq org-agenda-log-mode-items (quote (closed clock)))
           (setq njn/org-agenda-show-closed 't)
           (message "Showing closed clock entries in agenda"))
    ))

Thanks,
--Nate