Notes about user exits (valid up to at least SAP release 4.0B)

One way to find user exits applicable for a given SAP screen. From the SE38 screen, enter the desired screen main program, and click Utilities > Find In Source Code, and "CUSTOMER-FUNCTION" as the text to search for. This will give you a list of the user exits and where they are called from for all screens in the module pool.

Note: format of ABAP statement is CALL CUSTOMER-FUNCTION '009', for example. This is the statement called by a submodule attached to the main program.

Actual related function is EXIT_SAPLCOIH_009, for example. This example refers to customer function 9 in main program SAPLCOIH. Not all user exit functions are names as such, but this is the usual format.

If you are doing data validation and want to set an error message with a field open, you must be sure that the user exit you are using is linked to a calling module in the PAI section of the screen and the field you wish to be open was in the CHAIN statement which caused the PAI module to be invoked.

If you use a customer function which was invoked by a PBO module to validate data, the "MESSAGE" statement will cause the screen to return with the desired message at the bottom, but with all screen fields closed for input.

When you make changes to the include module for a given customer function, you must regenerate the related function group before you will see the changes included in the screen behaviour.