I should add I would like not to search the whole site, rather just the specific address book or what have you.

I'm not sure if what you're trying to do is the right way.

I'm using the form block to generate a form and not to manage data. Thinking about an address book - you'd have to add some edit functionality too which doesn't make sense for a feedback form.

I think these are two different things...

You might have to build your own block for this I guess. It would be possible to use the form block and get the results using some simple sql statements but that's probably not the best way..

i think it'd just be a matter of updating the search index script to make sure it includes the content of posts from the guestbook if it doesnt already..

you can already limit the search to specific areas of the site, so that'd do the job - no?
-frz