What I was looking for was something similar to a custom task pane (in all
other apps), or form regions, but they appear to be only available in OL
2007. In my case, I want to add a form I designed to the message
view/task/calendar whatever, as well as the message itself if it is opened.

I am sure that it can be done, because I've seen addins which do this, but,
I fear it may be similar to the situation when I went to replace a washer in
a kitchen sink (I ended up with pretty much a new kitchen). In other words,
the effort to accomplish it led from one thing to another, and the effort
proved to be much more substantial then I had first thought.

I know there are some third party libraries that allow similar functionality
(AddIns Express). If anyone has any comments on that one specifically, I'd
be interested in hearing about it.

Thank you in advance

jf