How to create UPPERCASE formatted text field with mixed character input

[r00tb33r]

I am looking for a way to instantly format text that user types to uppercase. However the input will contain non-alphabet characters such as spaces and dashes. I tried JFormattedTextField with a long "UUUUUUUUUUUUUUUU" mask, but it is not able to handle non-alphabet characters.
For example format "bp96-00826a" into "BP96-00826A".
Is there a better or an easier way to do this than a document listener?
Document listener seems a bit of an overkill to do something so conceptually simple.
Thanks in advance.

[r00tb33r]

Actually nevermind, I couldn't figure out how to do it using DocumentListener.
I would get "Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Attempt to mutate in notification" every time I try to make the text uppercase inside the listener while the user is typing.
So I do need help, an example to be exact.
Thanks in advance!

[Fubarable]

Let's see your code.

edit: have you considered using a DocumentFilter instead?