"Documentation" to me means the API documentation for the GridBagLayout class.
So once again, if you have a question, try it first, don't assume it doesn't work.
This implies you have tested code and it doesn't do what you want.
And I have lost track of the number of times I have referred you to the Swing tutorial.
You can create a class to register text field you want to check and store the text fields in a List. You add a DocumentListener to each text field.