Surely the best way to achieve that would be to password protect the logon to your account and restrict the accounts available to only your own and the administrator accounts, etc. You can also set it up so that when it goes to screensaver, etc. that you need to enter your password when it resumes.
Keeping people out is preferable to checking to see if anyone has used it, that is to late.
Having found how to exclude the file, yet it doesn't work, sort of answers the question I asked but you didn't answer, e.g. does avast alert on the file ?
I suspect that it doesn't, so it isn't avast blocking as it isn't a blocker but a scanner, it will block and alert if an infected file is found.
The same with your comment "It wont even allow me to use a joke program that turns the screen upside-down, and I sometimes NEED that program."
What exactly do you mean by that is avast alerting on it ?
The thing is that I had no antivirus at all for about 6 months because I wanted to avoid these kind of things.
This could well be the true cause of the problem.
What other AV installed was in this system and how did you get rid of it ?