Change log in KNA1 for custom field

Hi All,

I have appended a custom (Z) structure in KNA1 to add 2 new fields in KNA1. Now my requirement is to activate the Change log for the two new fields. I had checked the option at data element level for 'Change Document'.

I had also tried changing/adding some configurations in BD50, BD61, etc randomly for achieving the same, but without success.

Can anyone tell the complete process for the same?
Is there any document/ white paper available for the same? please share.

Regards

Manu B