Is my mac being used?

Hi there,

I share an office and sometimes share my macs and i need to know how i can find out how often my system is used while i'm not there - is there a log file that will tell me exactly when my mac has been used?

I'm running two systems -
Mac Pro Quad 3 8G RAM - Leopard
G5 imac 1.8 20" 2G RAM - Panther

if there's different methods for each system then i'd like to know both please.

Many thanks

I'm not sure I understand... Used as someone else actually using your computer when you are not there?

If you make them use a guest account (that you would have to set up for them) there is parental options that will let you know how many times/how long they are on.

Here is an example on Leopard:

Thanks for your reply,
With these guest accounts you dont get all the administrative access right? Thats not going to work as both myself and the other user need full access to all system operations.
Basically i just wanted to know how long the other guy is spending on my system when i'm out, and also maybe how long i'm spending on it when i'm in.
Can i use the same method as you mentioned but with my administrator account? I'll check it out next week when i'm back in the office.
Cheers
Aarrgghh