Using FileMaker Pro Advanced > About custom functions (FileMaker Pro Advanced)
About custom functions (FileMaker Pro Advanced)
The Custom Functions utility lets you create custom functions that can be reused anywhere in the database file in which they are created. You can copy and paste custom functions between FileMaker Pro files or you can import custom functions from other FileMaker Pro files. Once a formula has been written or changed for the function, they do not have to be rewritten to be applied to other fields or used in other scripts.
Custom functions can be used:
anywhere in a file
by any user or only by users with full access privileges
across multiple platforms
to replace third-party plug-ins for some purposes
Custom functions will run in both FileMaker Pro and FileMaker Pro Advanced. Newly defined functions appear under their own category in the functions list of the Specify Calculation and Edit Custom Function dialog boxes. If you do not wish to reveal your custom functions, you can disable their display in these dialog boxes.