Custom functions are procedures you create in Crystal Reports to evaluate, make calculations on, or transform data. When you use a custom function in a formula, all the operations in its definition are performed without you having to specify them individually in the formula itself. Thus, the custom function provides a way for you to share and reuse formula logic which, in turn, makes it easier and less time consuming for you and your users to create reports.
For example, suppose you are designing a series of reports from a database that stores department information with three-letter code names, but you want the actual department names to appear in your Crystal reports. Creating a formula to transform the data would work, but you'd have to copy the formula logic from report to report until you'd completed the series. It is much easier if you extract the logic that does the data transformation and save it as a custom function. You can add that custom function to each report in your series without having to reenter the text.
Note A custom function cannot be placed directly in a report; it must be used as a part of a formula.
Advantages of Using Custom Functions | Custom Functions Work Flow | Creating Custom Functions | Basic Syntax for Custom Functions | Crystal Syntax for Custom Functions