I want to use Exel.vba to create a Log In / Timesheet.

Primary question: Can VBA do this? or do I need to buy VB? or can I declare
a C++ function to do this?

I am unclear how to create these Subs: (Can I do any of these under Excel
10.0's VBA?)
1) I need a workbook to Open when the user unlocks thier computer. (most
users don't log off)
2) The Application would be perfered to stay hidden until they activate it
by clicking on a systray icon.
3)When the user locks thier computer (or logs off, or shuts down), I need
the app to mark the time it happened.