robahas on "[Plugin: Contact Form 7] Can't get anything out of the wpcf7_bfore_send_mail action hook"

HI - I've been fighting with this for several hours. I see various examples online about how to use this action hook, but when I use it in funcionts.php it never does anything. I even set up a fresh install of WP just to test this.

Here is my latest attempt

function wpcf7_do_something (&$WPCF7_ContactForm) {
    $wpcf7_data->skip_mail = true;
}
add_action("wpcf7_before_send_mail", "wpcf7_do_something");

What am I doing wrong? Should I not be using functions.php?

Thank you!

http://wordpress.org/extend/plugins/contact-form-7/