file-access at interrupts

There are many TSR Anti-Virus programs that checks many files in the
background. How can I write a TSR Turbo-Pascal 7.0 program, that have
file-access at an interrupt? Is this available?
If you may send me a little example, then I'm very happy!

Thank you very much.

-----== Posted via Deja News, The Leader in Internet Discussion ==-----   Now offering spam-free web-based newsreading