$do_not_duplicate and functions.php

I’ve got some additional front-page loops being called from my functions.php file via my theme, and they’re working great. Only trouble is I don’t seem to be able to get my actual main loop template to respect the do_not_duplicate array. This is the code I’ve got now, which is very wrong somehow:

In functions.php:

global $do_not_duplicate;
$do_not_duplicate = array();

function latest_template($category){
if (is_front_page() && !is_paged()){
$temp_query = $wp_query;
$my_query = new WP_Query('category_name='.$category.'&posts_per_page=4');
	// Start of 'The Loop'
	if(have_posts()){
  while ($my_query->have_posts()) : $my_query->the_post();
		 $do_not_duplicate[] = $post->ID;

[etc., to the end of the latest_template function]

In the post loop template:

global $do_not_duplicate;
// Start of 'The Loop'
if (is_front_page()){
	query_posts(array('post__not_in'=>$do_not_duplicate));
	}

if(have_posts()){
while (have_posts()) : the_post();

All the posts that are getting pulled in by the function in functions.php are also appearing in the loop, even though I have attempted to create a separate query for the front page that will exclude them.

I’m sure the problem is very elementary, but I’m not very strong in PHP and globals are a little over my head (apparently), so I haven’t been able to spot the problem. Can anyone point me in the right direction?

Thank you!