Callback of formular fields

I suggest to implement the following feature:

The idea is to get a callback, when a formular field get’s changed its value. To interact with parameters for example

A typical use case might be:

The idea could be: When a checkbox get’s checked, than a text field could be forced to have an user input, when the checkbox get’s unchecked, then the textfield could also be empty.
This would be a very important feature to fully control predefined PDF’s

THX