BlockUI - unblock when clicking blockOverlay - bindEvents, false

BlockUI - unblock when clicking blockOverlay - bindEvents, false

I'm trying to use BlockUI in a similar way to a lightbox.
The page displays a sign-up form and blocks everything else on the page to allow them to fill in the form and submit.

I've have a button in the unblocked content that issues an unBlockUI.

All working well but it would be good if they clicked on the overlay area for this to also unblock. Specifically the div.blockOverlay.

In the docs:
http://www.malsup.com/jquery/block/#options

// enable if you want key and mouse events to be disabled for content that is blocked
bindEvents: false

Setting this to false still captures all mouse clicks. Is there a way to bind an event to blockOverlay so I can use unBlockUI?

Thanks.