Skip proceed and go to checkout when appointment is confirmed

Hi, I would like to skip the proceed link and go to checkout when appointment is confirmed. I am using App+ and Marketpress. I tried the code for functions.php on this thread but it creates some weird loop effect on my side: https://premium.wpmudev.org/forums/topic/skip-straight-to-checkout-when-appointment-is-confirmed#post-961765

I have given staff access to the site in question.