"Top" records and summing remaining records

[jmiller]

What is the best way, if it is at all possible to do the following using the designer?

I want to create a report that shows the last 3 open invoices. If there are more than 3 than I want a total of all of those.
Due Date Amount
====== ======
2011-05-01 100.00
2011-04-01 110.00
2011-03-01 120.00
2011-02-01 130.00
2011-01-01 140.00

I would like the report to look like:
Due Date Amount
====== ======
2011-05-01 100.00
2011-04-01 110.00
2011-03-01 120.00
(PRIOR) 270.00
-------------- ----------
TOTAL DUE 600.00

[Alex K.]

Hello,

Please see the sample report in attachment.

Thank you.