Tracking flexitime using Emacs (& org-mode)

Question

So, at work we use flexitime (flex hours, flexi hours...) which is nice but can be hard to keep track of. I'm currently using org-mode to keep track of my hours (org-clock-(out|in)) but I'd like to extend that to automagically calculate if I've worked more than 8 hours (surplus time should be added to my flexitime 'account') or less (depending on how long lunch break I took etc), the balance on my flexitime 'account' and such.

Does anyone else use Emacs for this?

I'm currently using a very basic setup to track my time:

(defun check-in ()
  (interactive)
  (let (pbuf (current-buffer))
    (find-file (convert-standard-filename "whatnot"))
    (goto-char (point-max))
    (insert "
")
    (org-insert-heading)
    (org-insert-time-stamp (current-time))
    (org-clock-in)
    (save-buffer)
    (switch-to-buffer pbuf)))

(defun check-out ()
  (interactive)
  (let (pbuf (current-buffer))
    (find-file (convert-standard-filename "whatnot"))
    (goto-char (point-max))
    (org-clock-out)
    (save-buffer)
    (switch-to-buffer pbuf)))

question from:https://stackoverflow.com/questions/10122813/tracking-flexitime-using-emacs-org-mode