Enable reference problem

Hi to all,

I'm trying to enable/disable a field depending on to another field (if field 'A' is null, field 'B' is disabled and vice versa). I have completed enable_ref attribute on GET_DEFINITION method of my UIBB form and it works at beginning but when I fill field 'A', field 'B' is enabled but without matchcode.

I have tried it changing disable attribute and other similar ones but I haven't gotten lucky to find a solution for this problem. Any suggestion / comment will be appreciated

Thanks in advance and best regards.