Croquet

I live in Sarnia, Ontario, Canada, which is on the border between Canada and US, across the river from Port Huron, Michigan. When I use the 100 mile radius search feature for local caches, it gives me Michigan ones too (the majority). Crossing the border to geocache is not something I would very often want to do. Is there a way to only search Ontario caches within 100 miles of my location? Right now you can't say both 100 mile radius AND Canada.