Connecting your Computer time.

I run both Mac and Windows XP on my Computer. I'd like to see a feature that would combine the time of both, operating systems so I can Compare. Sorta like having a category displaying each application and how much time you use it on both operating systems. Than have a comparable feature for instance, lets say I use Firefox on Mac for 34 minutes, and I use Firefox on Windows XP for 28 minutes, I'd like to see the ability to compare both, from either side of the operating system.