filterText.addKeyListener(
new ExpressionRuleContext(filterModel, filterText));
filterText.getDocument().addDocumentListener(
new DelayedFilterTextDocumentListener(filterText));
filterCombo.setEditable(true);
filterCombo.addActionListener(
new AbstractAction() {
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("comboBoxEdited")) {
try {
//verify the expression is valid