You must write all custom programs to accept one or more parameters. User Exits describes these parameters.

Custom programs are executed within the flow of the standard programs. If your program displays any frames to the user, make sure that the way they are displayed does not interfere with the standard functions. Two important rules to follow are:

When batch processing occurs, a custom program should not solicit input from the user. The only interface should be messages. This rule applies to three of the user exits in Call Activity Recording that occur during inventory processing. These exits are numbered 50, 55, and 60.

Also, for the custom program to be found, make sure it resides in an appropriate directory in your propath. The system looks for the program in a directory that matches the first two characters of the program name. For example, place a program named fscustom.p in the .../fs directory.