Even though your combine sat for only 2 weeks,it would have been when mice were actively searching shelter for the winter,and yours with grain still in it looked like a great place. It is tough to keep the critters out.For long term storage,the first thing is to clean it as good as possible.I spend at least a day on mine with an air compressor,leaf blower,vacuum ,and garden hose.Amazing how many out of the way places can trap dust and chaff for nests.When I am done,you could eat off the frame in most places. The grain tank should be vacuumed out under the augers.Not fun,but need to eliminate all the food sources possible.Same with the clean grain and tailings augers.I park the combine on as much slope as possible and try to swish them out down through the seives.Same with the auger bed.Take the cover off the outside at the bottom and wash all that stuff out good.It needs to be kernel-clean.No food supply-no problem usually. The other fellows are right about the dryer sheets and Fresh-Cab pouches becoming food or nesting materials.They need to be rotated when they lose their effectiveness. Try to fight mice with their own keen sense of smell and habits.That's why mothballs work,and I have tried sprinkling black pepper throughout.I have heard of guys spraying the insides with diesel fuel after cleaning.Mice will get the oil on their feet and fur,and since they work at cleaning themselves,won't like the taste. Try to look at how the mice get in.Crawl up the tires I guess.Maybe the mothballs need to be spread on the ground around and under the combine.Just my thoughts since I can't sleep.Good luck.