Centering Input Boxes - Auto Allowing The Content To Scroll Left And Right?

I have a div that is set to overflow auto allowing the content to scroll left and right. This is because the content I am putting in it (a series of input boxes) is considerably wider than the containing div. The way it sits, when I start in the first input box and continually tab to the other input boxes, the focus goes from the left of the screen to the right. Once it hits the input box to the right of the screen, some of the input box is hidden to the right. As I tab to the input boxes to the right, each one has a portion of the element cut off by the view window.

What I want to happen is when I start at the left most input box and tab over, as I reach the center of the viewable part of the container, I want the input boxes to continue to center themselves until I reach the last ones. I think that telling each input box to center itself in the visible window of the containing div as it gets focus would work, I just don't know if there is an easy way to accomplish this using javascript I am using the mootools framework if that helps my case any.