Every time I try to use Excel or Word after a few seconds it closes (without saving) my documents. This is a relatively new occurrence and I’m pretty sure it’s related to my Avast - please could someone advise me how to stop this happening? 
How do you know it’s Avast related?
Any error messages, what does your event viewer show?
No such problem here and I use Avast and Office.
We need more information if you want help.