use the CONCAT function in the SQL for rsGchild recordset.
SELECT cars.Model, CONCAT(cars.From_dt, '-', cars.To_dt) as FromToDate
FROM cars
ORDER BY cars.From_dt
the FromToDate column wont be availabel for selection in the Create Dynamic Array wizard, but you can change:
echo "WAJA[".$n."][".$m."][1] = "."'".WA_DD_Replace($row_rsGchild["From_dt"])."'".";\n";
to:
echo "WAJA[".$n."][".$m."][1] = "."'".WA_DD_Replace($row_rsGchild["FromToDate"])."'".";\n";