InfoPath Dev

I have a SharePoint library whose form has a repeating table in it. I'd like to use a new form to retrieve data from all the completed forms' repeating tables so I can report on the data. The form is a modified version of the Agenda form that came with SharePoint.

 We use it for Action Items and I'd like to report on each form's open action items using a new form. How do I collect and filter that data?

You have come upon a common issue I have seen is how to aggregate form data for multiple forms.  SharePoint has limitiations here, since it does not store the data relationaly and it will only work with 100 forms at a time.  You may be able to do something with merging but with repeating data especially, it is not very clean.

This is one of the issues the Database Accelerator was created to address.  It enables the forms to be databased and data to be injected into a SQL table for SQL reporting or a Sharepoint Gadget or whatever. I would recommend trying the free download.  For enterprise form solutions, like it appears you are creating, it is a must.  It makes creating secured forms, with dynamic content, and reporting very easy.

Qdabra Database Accelerator Suite Version 2.0 - Developer