Trigger when adding, editing or deleting from table
When adding, editing or deleting from a table (collection) in a form, you should be able to trigger rules and do refresh on some UI controls.
The edit and delete functions have an option to execute a validation rule. This can be used as a trigger but from the documentation and forums it seems to be discouraged.
Even if you use it to change values (not just validate), you can´t execute refresh or things like this in actions & validations.
When validating on edit you should be able to read the old and new values.
When validating on delete you should be able to read the collection with and without the deleted record.