QComboBox relational sql table

Salutations, I've search around but no success. Do you guys know how to use relations with QComboBox? I simply need to retrieve data using the selected item, I'm currently using QSqlQueryModel as model, but it doesn't fulfill my needs. I know how to use QSqlRelationalTableModel with QTableView, but as I said, I'm needing to use relations with QComboBox this time... I hope anyone can help me, thanks in advance, and sorry for my bad english. :o

And another question.. how do I `refresh` a view, so it reloads the model that has been recently changed and submitted so it can show the new items normally? ;)