I am on my way but it's quite dificult to find out without your system 
Questiosn:
1- How did you enhance the BOL with the new field?
2- In this piece of code with which value is filled? (an example of debugging)
IF <nval> <> <oval>.
current->set_property(
iv_attr_name = 'ZZCR_AT' . iv_value = <nval> ).
ENDIF.
3- Can you paste the code of the GET?