Now I have an answer:
If I write the script DDL like the next, then now yes it work:
CREATE TABLE demo(
idcad CHAR(2) CHECK (SUBSTR(idcad, 1, 1) IN ('0', '1') AND SUBSTR(idcad, 2, 2) IN ('1', '2', '3', '4', '5'))
);
But still I have a doubt. I can define on InterBase sets of characters like...