code: private void addClickHandlerToCheckBox(final CmsCheckBox check, final Widget unzipWidget, final CmsFileInfo file) {
  
          check.addClickHandler(new ClickHandler() {
  
              /**
               * @see com.google.gwt.event.dom.client.ClickHandler#onClick(com.google.gwt.event.dom.client.ClickEvent)
               */
              public void onClick(ClickEvent event) {
  
                  // add or remove the file from the list of files to upload
                  if (check.isChecked()) {
                      getFilesToUpload().put(file.getFileName(), file);
                      if (unzipWidget != null) {
                          enableUnzip(unzipWidget);
                      }
                  } else {
                      getFilesToUpload().remove(file.getFileName());
                      if (unzipWidget != null) {
                          disableUnzip(unzipWidget);
                      }
                  }
  
                  // disable or enable the OK button
                  if (getFilesToUpload().isEmpty()) {
                      disableOKButton(Messages.get().key(Messages.GUI_UPLOAD_NOTIFICATION_NO_FILES_0));
                  } else {
                      enableOKButton();
                  }
  
                  // update summary
                  updateSummary();
  
              }
  
              /**
               * Disables the 'unzip' button
               *
               * @param unzip the unzip button
               */
              private void disableUnzip(Widget unzip) {
  
                  ((CmsToggleButton)unzip).setEnabled(false);
              }
  
              /**
               * Enables the 'unzip' button
               *
               * @param unzip the unzip button
               */
              private void enableUnzip(Widget unzip) {
  
                  ((CmsToggleButton)unzip).setEnabled(true);
              }
          });
      }
docs: Adds a click handler for the given check box.<p>
  
  @param check the check box
  @param unzipWidget the un-zip check box
  @param file the file