I sympathize. We had an attic flying squirrel problem a few years back, which is good/bad news compared to the larger daytime critters. The flying squirrels aren't quite as destructive, but they're harder to keep out, only takes a half-inch opening. I trapped them, and then paid Critter Control to seal up everything. If you have gray squirrels, then there is an opening somewhere that should be visible. If you have gable vents, use heavy duty wire screen to block it. not the kind screen door stuff the builders usually put up there. Since gray squirrels are active in the daytime, they will not be there when work is going on to install whatever barriers are needed, or closing up holes. I get rid of them when I can in the back yard, but my safe shooting area is limited. Good luck.