thanks for your answer,but that work with data not filtered..i think.. i need that the combos go filtering for his parent this is the table structure

country:
id
country

providence
id
providence
idcountry

person.
id
name
idcountry
idprovidence

when i setup the relation and push the combo providence its populate with all providence, and i need that populate with only the providence of his country parent

Thanks