The Widget or the Menu

I have the following code in my “header.php” file:

<div id=”header”> <!– header starts here –>
<div id=”theblogtitle”> <!– theblogtitle starts here –>
<h1>“><?php bloginfo(‘name’); ?></h1>
<div id=”theblogdescription”> <!– theblogdescription starts here –>
<h2><?php bloginfo(‘description’); ?></h2>
<div id=”navmenu”> <!– navmenu starts here –>
<?php wp_page_menu(‘show_home=1&menu_class=page-navi&sort_column=menu_order’); ?>
</div> <!– navmenu ends here –>
</div> <!– theblogdescription ends here –>
</div> <!– theblogtitle ends here –>
<div id=”widgetized-header”>
<?php if (function_exists(‘dynamic_sidebar’) && dynamic_sidebar(‘header’)) : else : ?>
<?php endif; ?>
</div>
</div> <!– header ends here –>

I am tryin to figure out (with no success, obviously) how can I display the code between the “navmenu” DIVs in the event that no widget has been placed in the “widgetized-header” area. In other words, I am perfectly happy with the “navmenu”. However, if I decide to use a widget to create a custom menu, I don’t want the “navmenu” to appear. I hope I’m making sense.
Any of your usual guidance is appreciated. Thanks!