The Custom Functions utility lets you to create custom functions that can be reused anywhere in the database file in which they are created. Once
formulas are written for the function, they do not have to be rewritten to be applied to other
fields or used in other scripts.
You can maintain and edit custom functions and the formulas they contain in one central location. Any change made to the custom function will be copied to all instances where that custom function has been used.
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.