Screen exits allow you to add your own fields to specified screens in standard transactions. In order to be able to use customer-specific subscreens, you have to create a project first. For further details, see Creating Additional Projects Then, you must include the SAP enhancement that contains the screen exit you want to use in your project. From the main screen of the Project management transaction, proceed as follows:
1. Select Enhancement components and choose Change.
The system lists all customer exits contained in the enhancements included in your project.
2. Place the cursor on the screen exit you want to create your own subscreen for.
3. Choose Edit component.
The system prompts you to enter a development class for your subscreen. Use the development class that contains all of the objects created for this specific enhancement project. The system then transfers you to the Screen Painter.
4. Create your subscreen using the Screen Painter.
5. Add modules to the screen flow logic as needed.
Enter the name of the module in the flow logic editor, then double-click on the module name and the system automatically creates the module in the corresponding function module program.
6. Generate your screen and choose Back (the green arrow) to return to the Project management transaction.
Once you activate your enhancement project, the fields defined in your subscreen will appear in the standard transaction.
When you use a screen exit, you need to be aware of how your subscreen and the fields it contains relate to the data on the standard screen. The global data defined in the standard SAP program is not known to the program that controls your customer subscreen. In the same way, the fields you use in your subscreen are not known to the SAP program in which they appear. To compensate for this problem, SAP creates special flow logic modules when defining screen exits.
SAP creates a special Process Before Output module (PBO module) with a function module exit. You can use this function module exit to transfer specific field values from the SAP program to your customer subscreen. SAP also includes a Process After Input (PAI) module that has a function module exit for transferring values back from your subscreen to the SAP program.
The function module exits in these PBO and PAI modules are only activated if you create actual modules for each exit. For more information on how to create customer-specific function modules, refer to the section Creating Customer-Specific Function Modules.
The import and export parameters for the PBO and PAI function module exits are predefined by SAP. As a result, you can only transfer values to and from your subscreen if they correspond to the parameters determined in the existing function module exit interface.