[Plugin: Fancybox] Call custom gallery from thumbnail click?

Hello people!

This is my 1st post, even though I’ve been wandering in this section for quite some time now 🙂 But I knew this day would happen, the day I couldn’t figure out something just by reading others’ posts!

So, here’s my problem:

I am using a theme for wordpress that has fancybox already included in it. Everything works fine, smooth and clean, the way it’s supposed to.
Now there is something I’d like to do, and unfortunately I don’t have the knowledge for it:

When clicking on the 1st thumbnail of my post (on the post page itself), a sandybox slideshow appears and displays all the thumbnails. Cool enough, but I’d like this slideshow to display more than just those thumbnails.. Something like 10 or 20 files maybe, hosted locally.

I believe there’s a way to do this, I found this code fragment on another forum, but just couldn’t make it work, no matter how hard I tried (I can more or less “read” codes, but writing it is not yet something I can do!)

http://stackoverflow.com/questions/8800152/fancy-box-how-to-show-slideshow-from-a-single-thumbnail

So yeah, to put things simply, I’d like my “post1” fancybox to display X pictures, other than the thumbnails. And also, be able to repeat this trick with X different posts, so I need to find a clean way to do it, not just some structure trick. I tried to include the above code in the html part of my post, but just didn’t work.

Feel free to answer! And let me know if you need something else!