Hello,
I think you have missed one line.Check the bold line.
gwa_fcat-col_pos = 2.
gwa_fcat-fieldname = 'ANZHL'.
gwa_fcat-seltext_l = 'NUMBER'.
gwa_fcat-outputlen = 10.
gwa_fcat--inttype = 'P'
gwa_fcat-do_sum = 'X'.
APPEND gwa_fcat TO gt_fcat.
CLEAR : gwa_fcat.
Thanks,
Abhijit Mandal