Running Total fields can be useful as
summary fields in Cross-Tab objects. Create your Cross-Tab as shown in
Creating a Cross-Tab report, but choose a
running total field as your Summary Field.
Note: You cannot use Running
Total fields as columns or rows in a Cross-Tab.
If you want a running total that totals
down the Cross-Tab's columns, you must sort the records in the Cross-Tab by
Column and then Row.