how to exclude certain pages

hi

i need to exclude pages 20,311 in sidebar.
i found this parameter :

<?php wp_list_pages(‘exclude=20,311’ ); ?>

but do not get where to paste it in.
Does it go into the sidebar.php? and if yes, where exactly?

Please help
thank you

this is my sidebar.php

<!– begin sidebar –>
<div id=”menu”>

<?php wp_register(); ?> <?php wp_loginout(); ?>

<?php /* Widgetized sidebar, if you have the plugin installed. */
if ( !function_exists(‘dynamic_sidebar’) || !dynamic_sidebar() ) : ?>

<?php wp_list_pages(‘title_li=’ . __(‘Pages:’)); ?>
<?php wp_list_bookmarks(‘title_after=&title_before=’); ?>
<?php wp_list_categories(‘title_li=’ . __(‘Categories:’)); ?>

<li id=”archives”><?php _e(‘Archives:’); ?>

<?php wp_get_archives(‘type=monthly’); ?>

<li id=”meta”><?php _e(‘Meta:’); ?>

<?php wp_register(); ?>
• <?php wp_loginout(); ?>
• ” title=”<?php _e(‘Syndicate this site using RSS’); ?>”><?php _e(‘<abbr title=”Really Simple Syndication”>RSS</abbr>’); ?>
• ” title=”<?php _e(‘The latest comments to all posts in RSS’); ?>”><?php _e(‘Comments <abbr title=”Really Simple Syndication”>RSS</abbr>’); ?>
• “><?php _e(‘Valid <abbr title=”eXtensible HyperText Markup Language”>XHTML</abbr>’); ?>
• <abbr title=”XHTML Friends Network”>XFN</abbr>
• “><abbr title=”WordPress”>WP</abbr>

<?php wp_meta(); ?>

<?php endif; ?>

</div>
<!– end sidebar –>