Hi BKVS,
You can use the set method of the field i, once you select the value in field i the corresponding set method will get triggered then using current entity set the field ii.
At the end of the field i set method you can find something similar to current->set_property( iv_attr_name = 'field i' value = <new> ).
use the new value to findout the corresponding text value and set the value to field ii.