'Last Opened' date issue

I have a 2010 mbp running an up to date copy of Lion. I have an external HDD attached to a time capsule. I have only 5 root folders on the drive - four of them have very few files and subfolders but one root folder has 2000+ subfolders with 200000+ files in these subfolders. The problem is that all the 'last opened' dates are the same on the subfolders. And when I open and add a file to the subfolder or modify an existing file, the last opened date is not updated upon exit. Any solutions or ideas?

The ultimate goal here to allow for sorting or arranging of the folders.