Progress bar ideas (not file upload)

I am working on an import operation that takes 30-60 seconds. It
includes parsing XML, committing objects to database tables, etc.
There’s a lot of data in each XML file, which accounts for the time.
I’d like to display a progress bar somehow, and be able to use some
mechanism to advance it as the import operations moves forward. The
import code is in the controller. I think I could add the progress bar
to the import form (use an ajax request to submit the form), but I’m not
sure how the controller could callback into the progress bar.

Any thoughts?
-Kevin