We work a bit different. We use sales orders to forward a local order to our headquarters. When it is a new customer, the customer nr is empty (it's a customised field, not the account id). When our headquarters ackowledges the order to the customer, this new customer has a customer number. 

When we change the order status to acknowledged, we know there is a customer number. So when the status changes, I want to have an alert or popup that we have to fill in the new customer number in the account record.

I wrote the script checking the order status AND if the field customer number is empty in the account record, which works. Only I can't get a pop up. Alert doesn't work, and "info" is only for debugging.

Any ideas?