FileMaker Pro 10: The Missing Manual

Chapter 12. Extending Calculations

As you’ve seen in the past three chapters, FileMaker’s calculation functions can do everything from text processing to financial analysis. Since calculations show up in so many different places in FileMaker, you might want to use the same calculation more than once. It would be a shame to have to type it in every time—and then make changes in several places the next time you need to modify it. Or maybe you need a function or a feature that doesn’t exist in FileMaker.

For these situations and more, FileMaker provides two ways to extend the calculation system. The first, called custom functions, lets you design your own calculation functions. You can then use these functions in any calculation in the same FileMaker file.

The second way is more complex, and thus more powerful. You (or someone you hire) can create a FileMaker plug-in in a programming language like C++. The plug-in also adds new functions to FileMaker’s Specify Calculation window. The difference is that those functions can do anything a programmer wants them to do.

Note

To create custom functions or plug-ins, you need FileMaker Pro Advanced, a special version of FileMaker that has extra tools for developers. (Find out more in Chapter 19.) Once you’ve created a custom function or plug-in, though, it can be used in any version of FileMaker. Read on to find out more.

Custom Functions

You may create a custom function for many reasons. First, you might find yourself using the same calculation ...