how can I set "folder" dimmed in Menu Bar ???

As we know, in UIQ application in menu bar there may be the basic folder system or the extended folder system. Now I don't want it to be available in my application, then I can set it dimmed in the resource file.
But if I don't want to do like that, instead I want to set it dimmed by writing some code in my program, so how can I do ?
After you read the following you will understand my puzzle:
RESOURCE MENU_BAR r_exappsendas_menubar
    {
    titles=
        {
        MENU_TITLE
   {
   menu_pane = r_exappsendas_app_menu;
   txt = STRING_r_exappsendas_app_menu;
   },
  MENU_TITLE
   {
   menu_pane = r_exappsendas_edit_menu;
   txt = STRING_r_exappsendas_edit_menu;
   },
  MENU_TITLE
   {
   menu_pane = r_exappsendas_folders_menu;  
   DECLARE_CATEGORY_MENU_TITLE;
   }
  };
    }
 
then I can set "edit" menu title dimmed after executing the following code:
CEikMenuBar* menuBar = ((CEikonEnv*)iCoeEnv)->AppUiFactory()->MenuBar();
menuBar->SetTitleDimmed(1,ETrue);
But how can I set "category menu title" dimmed ?If I use menuBar->SetTitleDimmed(2,ETrue);
Then the system will throw out a panic: EIKCOCTL 25 (Index out of range in CColumnListBoxData)
So who can help me to solve the problem ?