warningThresholdField.addKeyListener(this);
        thresholdPanel.add(warningThresholdField);
        assertionPanel.add(thresholdPanel);
        // file panel
        filePanel = new FilePanel(JMeterUtils.getResString("html_assertion_file"), ".txt"); //$NON-NLS-1$ //$NON-NLS-2$
        assertionPanel.add(filePanel);
        mainPanel.add(assertionPanel, BorderLayout.NORTH);
        add(mainPanel, BorderLayout.CENTER);
    }