QSqlTableModel  filter not working?

Hi!
I created a QSqlTableModel, set a filter and used a QTableView to show a table of my filtered data. This works as expected...
model = new QSqlTableModel; model>setTable("XXX"); model>select(); model>setFilter(filter); table = new QTableView; table>setModel(model);
However, when I try to compute the sum of all visible values of a column in the table view...
float sum = 0.0f; for(int i=0;i<model>rowCount();i++) sum += model>record(i).value("amount").toFloat();
... I get the sum of ALL entries in the table model, NOT only of those items visible in the TableView (where the filter is applied).
How can I make my sum()function to compute the sum of only those values which are visible in the TableView?
Thank you for your answers!