Custom Prompts Dialog

We are running BOXI 3.1 SP3 Java, and we have an application that includes the Analytical Reporting and OpenDoc war files to display webi reports in our own portal. We would like to customize the prompts dialog to do advanced date handling and more powerfull cascading prompts.

Is there a way to replace the existing prompt dialog with our own page using Extension Points? We don't need to change any other part of the webi report viewer, so I really don't want to have to create a full SDK solution for viewing reports. Plus it would be nice to not have to hack the Analytical Reporting code so when new service packs come out we can upgrade without having to worry about our changes. Has anyone done this?

Thanks

Tim