DOCBOOK-APPS: how to comment programlisting or source code

i asked this question before and remember getting a response, and
managed to lose it somewhere.

  for the time being, i'm just generating HTML from my docbook source,
writing courseware manuals.  i'd like to comment the lines of source
code that i include (most likely in a <programlisting>) so that the
comments are nicely lined up (left-justified) and in italics.

  i know -- i can't actually say italics, so i'd probably tag the
comments as, what, lineannotation?  but it's the lining up that i don't 
know how to do.

  any helpful hints?  i'm still looking for that previous response ...
argh.

rday