The AdvancedDataGrid control extends the capabilities of the standard DataGrid control to improve data visualization.
One of the most important aspects of the AdvancedDataGrid control is its support for the display of hierarchical and grouped data.
Hierarchical data is data already in a structure of parent and child data items. Grouped data is flat data with no inherent hierarchy. Before passing flat data to the AdvancedDataGrid control, you specify one or more data fields that are used to group the flat data into a hierarchy.
The Flex 3 DataGrid control supports footer rows, so I am sure that the AdvancedDataGrid control would be able to do the same.
DataGrid footer example