Calculate height of absolute divs (JQuery)

I am using this script http://benholland.me/javascript/how-to-build-a-site-that-works-like-pinterest/ to create a gallery for a website.

I represent "blocking" divs inside another div that has its relative position (lets call it a "block holder"). The problem is that I cannot get the "holding block" to wrap around these "blocks" because they have an absolute position. My only option is to calculate the height of the tallest column with JS and transfer it to the CSS class.

Do you have any idea how to do this?