List<IForm> viewStack = getDesktop().getViewStack();
for (IForm f : viewStack) {
  if (IForm.VIEW_ID_N.equals(f.getDisplayViewId()) || IForm.VIEW_ID_S.equals(f.getDisplayViewId())) {
    f.doClose();
  }
}
BigForm f = new BigForm();
f.startModify();
f.activate();

...
  private ArrayList<IForm> formIds = new ArrayList<IForm>();
...

  public class NewHandler extends AbstractFormHandler {

    @Override
    public void execLoad() throws ProcessingException {
      INewFormService service = SERVICES.getService(INewFormService.class);
      NewFormFormData formData = new NewFormFormData();
      exportFormData(formData);
      formData = service.prepareCreate(formData);
      importFormData(formData);

      //Check the list of Form opened in position North and South to hide
      IForm[] viewStack = getDesktop().getViewStack();
      for (IForm f : viewStack) {
        if (IForm.VIEW_ID_N.equals(f.getDisplayViewId()) || IForm.VIEW_ID_S.equals(f.getDisplayViewId())) {
          formIds.add(f);
          getDesktop().removeForm(f);
        }
      }

    }

...

  @Override
  protected void execDisposeForm() throws ProcessingException {
    //Check the list of Form opened but hide to show again
    if (!formIds.isEmpty()) {
      for (IForm f : formIds) {
        getDesktop().addForm(f);
      }
    }

  }