Using supplemental fields
If your FileMaker Pro file accesses data from an ODBC data source, you can use supplemental fields to define unstored calculations or summary instructions that act on data coming from the external sources. These fields display calculation and summary results in the FileMaker Pro file without changing the external database. For example, you can use supplemental fields to display aggregated data from an external file similarly to how you use summary fields to display aggregated data stored in FileMaker Pro files.
You can define supplemental fields in the ODBC table for which you want to calculate or summarize values. See Defining calculation fields and Defining summary fields.
Related topics 
Placing and removing fields on a layout
Editing ODBC data sources