Advanced Topic: Creating a listener for a combobox in RPE

I have written javascript code that uses javax.swing to create a popup that contains a number of combo boxes.  I now need to create a listener for one of the combo boxes.  I have tried using the typical Java coding of private void listenerName, but when I do this, I get an error that "identifier is a reserved word".  If I remove the "private", I get the error: missing ; before statement.  Has anyone used Java Swing to create dialog boxes in RPE?  If so, could you please help me figure out how to set up a listener function within the JavaScript Code element.

Chris