23 Dropdown list box in selection screen

To create a dropdown list box on an ABAP selection screen, you must declare a PARAMETER with the AS LISTBOX addition and then populate its values using the function module VRM_SET_VALUES during the AT SELECTION-SCREEN OUTPUT event. Core Implementation Steps Define the Parameter: Use the AS LISTBOX and VISIBLE LENGTH additions to specify the dropdown field. Declare VRM Data Structures: Include the TYPE-POOLS: VRM (in older versions) or use the VRM_ID and VRM_VALUES types to hold your list entries. Fill Values: Populating the list is typically done in the AT SELECTION-SCREEN OUTPUT event, which acts as the PBO (Process Before Output) for selection screens. Assign Values: Call the VRM_SET_VALUES function module to link your internal table of values to the parameter ID.