Hello, i want to set a dropdown control which has the same type dependency of the grid's source

this is the detail:

$id = intval($_GET["rowid"]);

$g->select_command ="SELECT * FROM pagos WHERE idemp = $id";

$g->table = "pagos";

$col = array();
$col["title"] = "Id";
$col["name"] = "idpag";
$col["fixed"] = true;
$col["width"] = "33";
$col["align"] = "center";
$col["show"] = array("list"=>false,"edit"=>false,"add"=>false,"view"=>false);
$cols[] = $col;

$col = array();
$col["title"] = "Alumno";
$col["name"] = "idalu";
$col["fixed"] = true; $col["width"] = "44";
$col["align"] = "center";
$str2 = $g->get_dropdown_values("select distinct id as k, name as v from alumns where idemp = $id");

the dependency of this last line no works…. any ideas????