please read the SAP documentation, may be you will get more info,
- USEREXIT_FIELD_MODIFICATION
This user exit can be used to modify the attributes of the screen fields.To do this, the screen fields are allocated to so-called modification groups 1 - 4 and can be edited together during a modification in ABAP. If a field has no field name, it cannot be allocated to a group.The usage of the field groups (modification group 1-4) is as follows:
Modification group 1: Automatic modification with transaction MFAW
Modification group 2: It contains 'LOO' for step loop fields
Modification group 3: For modifications which depend on check tables or on other fixed information
Modification group 4: is not used
The FORM routine is called up for every field of a screen. If you require changes to be made, you must make them in this user exit.
This FORM routine is called up by the module FELDAUSWAHL.
See the Screen Painter manual for further information on structuring the interface.
You may also try the below user exit whether it meets your requirement as you want to process data at item level,
- USEREXIT_MOVE_FIELD_TO_VBAP
Use this user exit to assign values to new fields at sales document item level. It is described in the section "Copy customer master fields into the sales document".
The user exit is called up at the end of the FORM routine VBAP_FUELLEN.
Bluesky
