Photo Gallery - Different Width on Images?

Hi! Im quite new to AS and Flash and excuse my english Im not so good at it.

I needed to make a photo gallery and found a good tutorial here on Kirupa.com,
(Photo Gallery Using XML and Flash).

Everything went smooth and I understand some of the codes. The only problem I have is that my images have different widths so some images are centered while some are aligned to the left. I want every image to be centered. So I tried to change the movieclip position but I cant seem to get the point that decides where the images position are centered so all images are in the middle. They seem to always have the upper right corner as the point that decides how the images are positioned. I want the point to be in the middle. :stare:

I hope I can get some help if anyone understand what my problem is.
Thank you!