Sum of values

I see that
http://xlinesoft.com/phprunner/docs/how_to_calculate_values_on_the_fly.htm
i change it to following but cannot get the sum of values price + quantity correctly:
var ctrlPrice = Runner.getControl(pageid, 'Price');
var ctrlQuantity = Runner.getControl(pageid, 'Quantity');
var ctrlTotal = Runner.getControl(pageid, 'Total');
function func() {
ctrlTotal.setValue(Number(ctrlPrice.getValue()) + Number(ctrlQuantity.getValue()));
};
ctrlPrice.on('keyup', func);
ctrlQuantity.on('keyup', func);