DeWayne,
I don't think you can map a key to a non-displayable character, but you can change the translation table. Check your connection settings and select 3270 emulation tab. I think you have your language set to "English (U.S.) (37)" on the one that is mapping the square brackets to x' BA' and x'BB'. Change it to Latin 1 (1047), which maps them to x'AB' and x'BD'.
Regards,
John
Regards,
John