You can add a user-defined function to an expression. If you enter a user-defined function when you manually create an expression, you must prefix the user-defined function with :UDF. When you create an expression with the Expression Editor, valid user-defined functions display on the User-Defined Functions tab. Use user-defined functions as you would any other function.

If you create a user-defined function, which is only usable in the Designer, the function only displays in the Designer.

When you select a user-defined function, the Expression Editor shows the function syntax in the following format:

For example:

When you add the function to the Formula window, the function includes the prefix :UDF, as shown in the following example:

When you validate the expression,

CDI-PC

does not validate the user-defined function. It only validates the expression.