Suppress user-prompting when calling commands in programs

[Thorsten Jolitz <tjolitz@gmail.com>]

Hi List, 

I often encounter user commands that do exactly what I want, and would
like to reuse them in a program, but they are not really written for
programmatical use, i.e. they prompt the user for information to be
stored in (local) variables, but don't expose these variables as
function arguments:

#+begin_src emacs-lisp
(defun foo (&optional arg)
  (interactive "P")
  (let ((bar (org-icompleting-read ...)))))
#+end_src

I guess thats because writing the interactive spec and binding keys
becomes so much simpler that way. 

Assuming `foo' can't be changed - is there another way to bind `bar'
before calling `foo' in a program rather than advising `foo' (with the
aim to suppress any user-prompting at all during the execution of
`foo')?

I seem to remember that a solution for this exists, but I can't find
it anymore. Thanks for any hint. 

-- 
cheers,
Thorsten