Centering images? In Photo gallery tutorial

Hello Everyone, I have been studying the tutorial in the special effects section titled “Create a photo Gallery” and understand the tutorial but am having a small problem with what I am trying to accomplish. I am creating a photo gallery with images of different sizes. For example, they are all the same height but vary in the size of their width because some are perfect squares(medium format) and some are Horizontal (35mm). I am trying to get the images to import to the movie clip in a centered position. Currently when i use this tutorial model, all the images I am using import left aligned, thus creating an odd layout.

Thanks in advance if anyone can be of help.
Junkyard Dog