Add an admin page, but don't show it on the admin menu

Question

I have a custom plugin 'Charts' that has it's own menu. In that menu are links to the 3 pages for the plugin - 'Charts', 'Add Chart' and 'Edit Chart'. However, I don't want to display the link to 'Edit Chart'.

Here is how I add the page in question -

$this->pagehook = add_submenu_page('charts', __('Edit Chart'), __('Edit Chart'), 'edit_charts', 'edit-chart', array(&$this, 'on_show_page'));

I've scoured the internet, and cannot find a way to do this (that works). It's possible to remove whole top level menus (not what I need), and you can remove individual entries from the $submenu global (but doing that also removes the registered capability), so no one can access the page -

global $submenu;
if(!empty($submenu['charts'])) : foreach($submenu['charts'] as $key => $page) :
        if($page[0] === 'Edit Chart') :

            /** Removes all permissions to access the page */
            //unset($submenu['charts'][$key]);              
            /** Removes the title, but the menu entry still exists, so it looks odd */
            $submenu['charts'][$key][0] = '';

        endif;
    endforeach;
endif;

I've looked in to hiding it via CSS, but can't see a way to do that through the HTML that Wordpress generates -

<li><a href="admin.php?page=edit-chart" tabindex="1">Edit Chart</a></li>

I've also considered jQuery, but that has similar limitations to the CSS route, plus I refust to believe that I am the only one that has ever wished to do this - there must be a way, I just can't find it!

Any hints and tips appriciated.

Thanks.