W.S. that starts and stops with "user activity"

[iftar]

Hi everybody,

I need to run a function when there is no user activity.(like screensavers)
I wrote my function and i want to run in a Windows Service.
How can i set up this situation?

My function will start when there is no user activity for 5 min
and it will stop when the user become active(moves mouse or keyboard)

I hope i am clear enough. This subject is very important for me.
Please help me