<?php

add_action("gform_post_submission", "gf_ga_tracking", 10, 2);
function gf_ga_tracking($entry, $form) {
    if($form['id'] != 2) return; ?><script type="text/javascript">
        jQuery(document).ready(function($) {
            _gaq.push(['_trackEvent', 'Newsletters', 'Signup', 'SidebarFooter']);
        });
    </script>
<?php } ?>