double vatPercentage = event.getDouble("vat_percentage");
double totalAmount = event.getDouble("total_amount");
double amountWithVat = totalAmount + vatPercentage/100 * totalAmount;
event.set("amount_with_vat", amountWithVat);
if(event.save()) {
saved = true;
} else {
errors += DBHelper.getNiceErrors(model);
}