Other option would be writing the Java Script in the Calculate event of the fields to sort/ group/ totalling the values. Since all of your reports use the same layout, it would not be that difficult to write the code. Propably if you check the PurchaseOrder.xdp form that comes with your Designer samples along with installation, you get some basic idea on how to calculate the values as you add more rows to the form.
If you still have issues, you can always contact me or the team on this forum.
Thanks for the helpful tips! We'll check into those.