Finding a file...

I have three hard drives attached to my iMac (all 0.5TB), one of which I use for Time Machine. The Time Machine disk has died and although I have backups of all my files on another drive so nothing has been lost, I HAVE lost the ability to incrementally search back through previous versions of my 'live' files.

The problem I have is that I need to check out some files that have been worked on over the past couple of weeks. However, at this point I'm not interested in 'created date', 'last modified date' or 'last opened date' options - is there a way I can find out if a file was 'used' (ie opened but not necessarily modified or saved) on a certain date? Sort of like a window-watcher kind of thing really.

I'm using 10.5 and I can't see a way of doing this in the search options - maybe some bright spark might be able to help me...