enhance the extrtact structure

hello,

i m trieng to upload the data in ODS. for which i want an additional field in my ODS(<b>sales doc type which is mapped with AUART of table VBAK</b>).To populate my ODS i m enhancing my function module. i m attetching the code.

case i_datasource.

types:begin of lst_vbfa,

lst_vbelv type vbfa-vbelv,

end of lst_vbfa.

data: l_wa_mc type mc12vc0hdr,

l_tabix type sy-tabix,

l_wa_vbfa type lst_vbfa.

when '2LIS_12_VCHDR'.

*find corresponding master data record

loop at c_t_data into l_wa_mc.

l_tabix = sy-tabix.

select vbelv from vbfa into l_wa_vbfa where vbeln = l_wa_mc-vbeln

and vbtyp_v ='c'.

select single * from vbak where vbeln eq l_wa_vbfa-lst_vbelv.

*fill additional fields with master data

if sy-subrc = 0.

l_wa_mc-zzauart = vbak-auart.

modify c_t_data from l_wa_mc index l_tabix.

endif.

endselect.

endloop.

this code is not working properly(i m not getting values of auart)

what is error in it.

if it is possible then plz sand me some example code