[O] org-dblock-write:myownfunc does not split my window?

[Martin]

Hi there:

Using a minimal example:
Creating an org file with somewhere:


#+BEGIN: myownfunc
#+END

And using scratch (or this email) with

(defun org-dblock-write:myownfunc (params)
  (interactive)
  (split-window nil -15)
  (insert "window should be splitted"))

This just inserts the text "window should be splitted" but does not
acutall split my window.

What am I doing wrong?  And how can I make it right?

Thanks,
Martin