How to assign a derived value to a field based on the other fields entered on the form

Asset tracking super user -> Define location form

We have requirement of assigning the Location code to adress1 || ' '|| address2, whenever they are entered or changed in the location form.

We have tried with form personalization, WHEN_NEW_ITEM_INSTANCE. This works fine in most cases. But does not work when address1 is entered and immediately record is saved.

WHEN_VALIDATE_RECORD does not fire on this form, hence cannot use this event.

Is there any other way of doing this in personalization.