If this is the main data source (i.e. the form is bound to the list), I don't think you'll be able to just submit a single row. It seems like you might be able to do this with some complex logic - just kind of brainstorming here, but I'd have my initial query and displayed rows bound to a secondary data connection to the same list.... then when the user clicks the "Submit" button in the row, I'd have rules that run the main data source query for just that item, update the fields in that item, and then submit the main data source.