Users Online?

I think I might have bitten off more then I could chew agreeing to do this project but I was hoping that I could get some ideas from you great users.
I am trying to develop a workbook that users at my job can basically click a button to let us know that they're online and click another button to let us know that they are offline. I was hoping that there would be an option that it would keep track of the time that the user is online so we can keep track of the time of our employees that work from home.

Is anyone out there done anything like this before or have any ideas for me?
All help is greatly appreciated.
Thanks
Nate

Mrice,
Thanks for your help, this looks almost exactly what I'm looking for.
I've attached an example for what I would like the worksheet to look like.
Unfortunatly I'm unfamiliar with the tools that you've used to create yours.

Would you be kind enough to take the example that I've attached and add the macros to it?

I'd like to learn about adding the username of the computer and how you created this. Could you please help me out or point me in the rite direction with keywords for searching for help.

All help is greatly appreciated.
Nate

Mrice,
This is perfect. Thanks.
Is there any way to have the time clock paste always on row 4 and have all the other rows drop down so you can always view the newest users online?
Thanks again
Nate

mrice,
Sorry, but I'm a little confused with your explination,
Where exactly in the macros should add extra info?
Nate