Update Pivot Table with New Sheets

I'm attaching the file that I need help with. When you open the file, it displays a dialog asking if you want to "View Data" or "Begin New Audit." If you click "View Data," it closes the dialog box. If you click, "Begin New Audit," it creates a new sheet based on a Master Sheet, and it names the new sheet based on the current date (in yyyymmdd format). The workbook contains a pivot table that needs to update with information from the new sheet. I can update the pivot table manually (I'm using multiple consolidation ranges), but I need to create a button that updates the table with the ranges from the new sheet when clicked.

I know the answer probably lies in using named ranges, but I don't know how to use named ranges with new worksheets. Please help!