You can get a Spiral Saw Bit and put it in your Dremel..
something like this http://www.lowes.com/ProductDisplay?partNumber=24594-353-SC4&langId=-1&storeId=10151&productId=3027817&catalogId=10051&cmRelshp=rel&rel=nofollow&cId=PDIO1
something like this http://www.lowes.com/ProductDisplay?partNumber=24594-353-SC4&langId=-1&storeId=10151&productId=3027817&catalogId=10051&cmRelshp=rel&rel=nofollow&cId=PDIO1