This is one of the key limitations of SharePoint Form Libraries - they don't support repeating structures within one form. My recommendation would be to have the form submit to two SharePoint lists before it submits to the SharePoint form library. You map the form info to one list and the repeating info to another list and then you should be able to hook up Excel to work with those lists. To map a form to a list requires code, or you can use Qdabra's qRules SubmitToSharePointList (Qdabra is the sponsor of InfoPathDev.com).
The other approach would be to use a tool to download the forms to your local machine and map to a SQL database. Qdabra has a free trial of DBXL Client which you can install and set up to synchronize forms down from SharePoint. There's even a form for generating reports on repeating data. You don't have to map to a database; the tool lets you extract repeating data from the XML directly. You can do all of this without purchasing a license (i.e. it's free), get your report and be done but some configuration is required.
Yet another approach is to use a Web service to map the data to a SQL database on your server and use the same tools to generate the report. Once again, the free trial should be sufficient here but it will require installing on a server in your domain, ideally the SharePoint box.
Sorry there's no out-of-box way to do it, but the above tools are well-documented and many people use them.