Update BBBNR International location no from Custom entity attribute

Dear Experts,

I have created a custom attributes for the field International Location number ZZBBBNR in entity BP_CUSGEN and also enhanced the structures CMDS_EI_VMD_CENTRAL_DATA_XFLAG & CMDS_EI_VMD_CENTRAL_DATA with the Z fields.

But we want to update the standard field BBBNR in table KNA1, so I have implemented the BAPI method IF_EX_CVI_CUSTOM_MAPPER~MAP_BP_TO_CUSTOMER and wrote the below logic to move the value from the ZZ fields to standard fields.

    c_customer-central_data-central-data-bbbnr = c_customer-central_data-central-data-zzbbbnr.

      c_customer-central_data-central-data-bbsnr = c_customer-central_data-central-data-zzbbsnr.

       c_customer-central_data-central-data-bubkz = c_customer-central_data-central-data-zzbubkz.

    c_customer-central_data-central-datax-bbbnr = c_customer-central_data-central-datax-zzbbbnr.

      c_customer-central_data-central-datax-bbsnr = c_customer-central_data-central-datax-zzbbsnr.

       c_customer-central_data-central-datax-bubkz = c_customer-central_data-central-datax-zzbubkz.

But the value is not updated in the KNA1 standard fields. Please give your valuable suggestions.

Thanks.

Nalla B