Once you get them out of your attic, you can get coyote urine at the farm store. They have perforated bottles that you can put cotton balls inside. Put a little of the urine on the cotton and hang them near the eaves of the house. It does a good job of keeping the squirrels from coming back. Also, trim any tree branches away from the house. Try and keep the branches 10' off the house. That will help keep the squirrels off the house too.