Events are not fired for Lookup Objects.
E.g. add an Event onblur (or any other event) in the "Custom Code" Tab with the Javascript:
alert('you will never see me!');
https://forums.nubuilder.com/viewtopic.php?f=19&t=10471
Not available!
Add events with JS or jQuery.
$('#your_fieldcode').on('blur',function() {
alert('You are going to see me!');
});