content before the more tag and functions.php

Hi,

I try to retrieve the content before the <!–more–> tag of a page.

I use a custom query and I created a specific function in my functions.php file.

Here is my custom query in my index.php page

<?php
		$arg = array('post_type'=>'page','post_parent'=>5, 'showposts'=>1, 'orderby'=>'rand', 'post__not_in'=>array(36));
		$randomService = new WP_Query($arg);
			while($randomService->have_posts()) : $randomService->the_post();
		?>
<!-- this is the function supposed to display the stuff -->
<?php the_page_excerpt(150); ?>

<?php endwhile; ?>

and this is the function in my functions.php file

function the_page_excerpt($length) {
	global $more;
	if ($pos=strpos($post->post_content, '<!--more-->')) { $more = 0; the_content(''); }
	else { $page_excerpt = $post->post_content; echo substr(strip_tags($page_excerpt),0,$length).'&nbsp;...'; }
}

But nothing displays… and if I add these lines in my index.php:

global $more;
	if ($pos=strpos($post->post_content, '<!--more-->')) { $more = 0; the_content(''); }
	else { $page_excerpt = $post->post_content; echo substr(strip_tags($page_excerpt),0,200).'&nbsp;...'; }

It works…

So, what is wrong with the function in my functions.php file?

Thanks a lot for your help!