User needs it in his footer so I think you should use conditional page logic. Something like:
If ( is_single(postID)) { //insert tracking code }
You can also use the post title or post slug, but id is the most reliable.
Old Answer
I would consider writing a shortcode. Add the following to your functions.php file. You can specify input parameters. In this case I specify id and target.
add_shortcode( 'signup', 'signup_shortcode' );
function signup_shortcode( $atts ) {
extract( shortcode_atts( array(
'id' => '',
'target' => '',
), $atts ) );
$HTML = 'hello world'.$id;
return $HTML;
}
Then call it in your post like so:
[signup id="1234" target="goog"]