The Summary function group provides
functions for creating summary fields such as:
Sum({Orders.Order Amount}, {Orders.Ship Via})
Summary fields are normally created by
inserting them from the Palette and modifying them in the
"Properties" view. They then appear in the
"Outline" view and can be added to a formula.
However, they do not need to be created in this way. You can create a summary
field exclusively for use by your formula by filling in the arguments to one of
the functions in the Summary functions section appropriately. However, any
groups in the report that the summary field refers to must already exist in the
report.