Load post with a different template

Hello,
Im using this code to load post with different template (for print version):
in functions.php

//add my_print to query vars
function add_print_query_vars($vars) {
    // add my_print to the valid list of variables
    $new_vars = array('my_print');
    $vars = $new_vars + $vars;
    return $vars;
}

add_filter('query_vars', 'add_print_query_vars');

add_action("template_redirect", 'my_template_redirect_2322');

// Template selection
function my_template_redirect_2322()
{
    global $wp;
    global $wp_query;
    if (isset($wp->query_vars["my_print"]))
    {
        include(TEMPLATEPATH . '/my_print_template.php');
        die();

    }
}

in my_print_template.php

<?php
    define('WP_USE_THEMES', false);
    echo "<h1>printer friendly version:</h1>\n";
    query_posts('p='.$_GET['pid']);
    if (have_posts()){
        while ( have_posts() ) { the_post();
            the_content();
        }
    }else{
    echo 'nothing found';
    }
?>

now all I have to do is create a link with ?my_print=$post_id in my regular single loop

Code working very good 100%

I would like use until five templates, my_print_template.php, my_print_template2.php, my_print_template3.php, my_print_template4.php, my_print_template5.php

How Can I do to redirect until five templates?