Contents of custom-menubar.php:
<div id="menubar-wrapper">
    <div class="menu-container">
        <?php
            if (is_home()) {
                wp_nav_menu( array( 'sort_column' => 'menu_order', 'container_class' => 'menu', 'theme_location' => 'MainMenu-Home' ) );
            } elseif (is_archive() || is_search()) {
                wp_nav_menu( array( 'sort_column' => 'menu_order', 'container_class' => 'menu', 'theme_location' => 'MainMenu-SearchArchive' ) );
            } elseif (is_page('about')) {
                wp_nav_menu( array( 'sort_column' => 'menu_order', 'container_class' => 'menu', 'theme_location' => 'MainMenu-About' ) );
            } else
                wp_nav_menu( array( 'sort_column' => 'menu_order', 'container_class' => 'menu', 'theme_location' => 'MainMenu-Other' ) );
        ?>
        <div class="clear"></div>
    </div>
</div>

Contents of functions.php in child theme:
register_nav_menus(array(
    'MainMenu-Home' => __('Main Menu - Home', 'easel'),
    'MainMenu-SearchArchive' => __('Main Menu - Search and Archive', 'easel'),
    'MainMenu-About' => __('Main Menu - About Page', 'easel'),
    'MainMenu-Other' => __('Main Menu - All other pages', 'easel')
    ));