Hello Abu. I have this situation: i fill a dropdown list in a grid (that is associated to a table "A" in the database) with values that are in a table "B". So when the user select a value in the dropdown list another fiels of that record in the grid update with values that are associated to the select value in the table "B". Up here everything works fine. Now i need to have this behavior but instead of use a dropdown list i want to use a combobox. So i can add new values in the field of the table A and not only does that are in the table B. How i do that?
Here is my code:

// Indico propiedades de la columna "predefinidos".
$col = array();
$col["name"] = "predefinido";
$col["title"] = "Predefinidos";
$col["resizable"] = true;
$col["edittype"] = "select";
# fetch data from database, with alias k for key, v for value
$str = $g->get_dropdown_values("select distinct tarea_predefinida as k, tarea_predefinida as v from tareas_predefinidas");
$col["editoptions"] = array
(
"value"=>$str,
"defaultValue"=>"No",
"onchange" => array
(
"sql"=>"select * from tareas_predefinidas",
"search_on"=>"tarea_predefinida",
"callback" => "fill_form"
)
);
$cols[] = $col;

….

<script>
function fill_form(data)
{
//jQuery("select[name=predefinido].FormElement").val(data[0].tarea_predefinida);
jQuery("select[name=anillado].FormElement").val(data[0].anillado);
jQuery("textarea[name=total].FormElement").val(data[0].total);

//jQuery("select[name=predefinido].editable").val(data[0].tarea_predefinida);
jQuery("select[name=anillado].editable").val(data[0].anillado);
jQuery("textarea[name=total].editable").val(data[0].total);

}
</script>

Thanks for your help.