orgmode developers and power-users,

I'd like to be able to declare custom entities (apologies if I'm using that
term incorrectly) within the text of an orgmode document which I can
specify custom formatting for when my .org is exported, e.g. to PDF or HTML.

I have a background in Docbook, so the analogue there would be defining a
custom xml tag and then extending the XSL files to handle it as desired.
Please see the following snippet:


* section title

Here is some text, but I want [specialthing: this bit here] to be formatted
differently than [newanddifferent: this other big over here].


Where I would have defined specific custom formatting rules for
"specialthing" and "newanddifferent" type entities.

Is there a way to do this in orgmode? If not, it seems like it would be a
very useful feature (at least to me:) ). Note: I don't care about the
syntax as long as the result is the same.

Thanks for your help,
~G
-- 
Computational Biologist
Genentech Research