[SOLVED]Horizontal scrolling

Okej.

I have tried to fix this for a whole day now.
I've made a photographer website, where he can upload pictures of a model in a administration tool. On the site, there will be thumbnails in the bottom. From the beginning, I told him that he can only put 5 pictures per model because It won't be nice to have a scrollbar.

Then I solved the scrollbar issue with Javascripting to make it look nice in both FF, Safari and IE.
But I can't solve one thing.
There are different number of pictures per model. I have a box containing the models, and I have a overflow:auto on this box.

If I don't create another box in this box with a fixed width on the box, the 6th picture comes below the other ones and it appears a vertical scrollbar.

So I created a box in the thumbnailbox with fixed width bigger than the thumbnail box, so that my horizontal scroller would appear. But then the models with only 3 pictures will have a horizontal scroller also, even if there are no pictures on the right.

I've tried to put width:auto; in the box inside the thumbnailbox, but the 6th pciture will come below the other five anyway.
I've tried dynamic CSS with PHP, but it doesn't work with FF.

I wnat to have a horizontal scroller IF NEEDED, to scroll only to the last thumbnail. Not more, not less.

can you please help!

The adress to the site is http://www.honerakrawi.com/BO/
Just press Enter and Agree first to see what I mean with the thumbnails.

Best regards
HuGoB