XD99 custom field mass maintenance doesn't work

Good morning to all,

I have a problem with maintenance of a custom field added to customer master (KNA1) with append. I want to maintain that field with XD99. In this transaction I can see the field and insert a value, but when I save, tha value is not saved.

I tried to create a new custom segment with my custom field and use BAdI CUSTOMER_ADD_DATA_BI, but before the call transaction to XD02 in the code, my field is empty. How can I maintain that field? Which method of BAdI CUSTOMER_ADD_DATA_BI should I use?

Thanks to all