Wordpress registration redirect priority - php

Question

I have asked this question but posted it incorrectly.
The following code redirects people to a custom page:
function possibly_redirect(){
global $pagenow;
if( 'wp-login.php' == $pagenow ) {
wp_redirect('https://www.mydomain.co.za/custom-page/');
exit();
}
}
I have added a custom login plugin but don't want it to pop up on registration negating the custom page. Is there a way to make the initial redirect happen first and prevent the registration form from loading?

Answer 1

<form method="post" action="<?php echo site_url('wp-login.php?action=register', 'login_post') ?>" class="wp-user-form">
<?php _e('Username'); ?>:
<input type="text" name="user_login" value="<?php echo esc_attr(stripslashes($user_login)); ?>" size="20" id="user_login" tabindex="101" />
<?php _e('Your Email'); ?>:
<input type="text" name="user_email" value="<?php echo esc_attr(stripslashes($user_email)); ?>" size="25" id="user_email" tabindex="102" />
<?php _e('Your pwd'); ?>:
<input type="text" name="user_pass" value="<?php echo esc_attr(stripslashes($user_pass)); ?>" size="25" id="user_pass" tabindex="103" />
<?php do_action('register_form'); ?>
<input type="submit" name="user-submit" value="<?php _e('Sign up!'); ?>" class="user-submit" tabindex="104" />
<?php $register = $_GET['register']; if($register == true) { echo '<p>Check your email for the password!</p>'; } ?>
<input type="hidden" name="redirect_to" value="<?php bloginfo('url') ?>?register=true" />
<input type="hidden" name="user-cookie" value="1" />
</form>