manipulating $theme.item.id in template file

hi all
I finally created a microthumb page navigation like on this page. http://pedrogilberto.net/gallery2/v/secret_places/3.jpg.html

I have 9 microthumbs showned and the problem is when I click on the sixth,seventh,eighth or ninth thumb
the thumbs move from their original places. I want to make them stay static, so I always tried to focus the thumb in the middle.

I have an algorythm where i try something like this before loading the thumbs, but the id did not change:
{assign var=$theme.item.id value= ID of a thumb in the middle}

So have anyone any ideas how to make the thumbs static and not moving from their places?