How to know the buffer I will return to from the minibuffer?

[Marcin Borkowski]

Hi all,

I am writing an interactive command to be used while in the minibuffer.
I need to know the buffer I was in when I issued the command that put me
in the minibuffer (like M-: or M-!).  I tried (other-buffer
(current-buffer)) and (last-buffer (current-buffer)), but to no avail.
Then I re-read the docs for `other-buffer' and used this: (other-buffer
(current-buffer) t), and it seemed to work.  The question is, how
reliable it is.  Am I doing this correctly?

TIA,

-- 
Marcin Borkowski
http://mbork.pl