I'm not finding any reference to an inurl parameter that can be passed, where did you read about this?
As far as I'm aware, you would need to prevent the pages from being indexed by the yahoo indexing service to prevent them from being returned by the Search for Boss search engine.
you can add the following meta tag to pages that should not be returned:
<META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW">
you will need to wait for the site to be re indexed for this to take effect though.