You always can use the "formatValue" to return input html to show text box at the cell of a table. And if the cell is inside a form then it can post back its value to server. At server-side you may get those value through $_POST. You may update database with:

$this->src("mysql")->query("update mytable set field1 = :field1, field2=field2 where ...")
->params(array(
    ":field1"=>$_POST["field1"],
    ":field2"=>$_POST["field2"]
))->start();

The start() method basically will trigger the query execution.

Note: KoolReport is designed specifically for reporting purpose, meaning that it focus on pulling data not pushing it. So the effect of above code is out of our expectation and design. We have not tested and there could be error.