Code to automatically close form lightbox once data submitted

Site URL: https://www.devonmind.com/training/mental-health-first-aid

Hi there,

I have several contact forms on my website which I have opening in lightboxes. Is there a way to add code that will close lightboxes automatically once data has been submitted by the user? Either in the post-submit HTML or code injection I guess.

Just click "Register your interest" on the link above to see an example. Entries just go to me, so feel free to test.

Thanks in advance! 

Andre