Hi jens,
AAAABB111 - 3 fields
AAAABB111222333444 - 6 fields
you can read AAA in Field_A and BBB Field_B.
and the rest read it in one field say Field_Sub = 111222333444.
try to populate number of occurrence in mapping.
correct me if i did not get you.
Regards,
Muniyappan.