Can someone give me guidance on generically catching input events for my application?

I need to calculate the idle time of the user. 

My first thought was to create a thread that runs and checks the last active time compared to the current time to 
determine idle time.

However, my issue comes in when I am attempting to set the last active time for the user.  I was planning on adding a 
function to set the time for all of the callbacks for every button in the application, but that seems like a lot to keep
 track of.

Is there a callback that I can set for the entire application, or atleast for every window, that will be called 
everytime the user provides input via the mouse?

Thanks,
Kendall