MM46 Mass Maintainence - Custom field issue

Hi all,

I have a requirement MM46 custom field ( with out ALE ) which would updates MARA - custom field value.

First step - Created custom field ( MARA-ZZXXX ) by using OMS9 trasaction for MM46 mass maintenance screen.

Second step - Created CMOD Z project.

In this step I got some confusion about writing the code for my Z field, Here I have found 2 include programs under EXIT_SAPL1001_003 exit

1. INCLUDE LXMGVF07 - In this include program I tried to create enhancement ( to write the code for my Z field by using WHEN C_PARNAM_CLIENTEXT ), but program is not allowing me to create enhancement / to change the include program.

System is giving " Changes to LXMGVF07 are forbidden by SAP"

2. If you double click on EXIT_SAPL1001_003 exit , here I have found INCLUDE ZXMGVU07.

In this include program I put break point, but this break point is not getting triggering / stopping.

Please help me on this