Welcome to FT, ilovesunshine!

The best tool I've found for segment runs is the old ITA search engine (matrix1.itasoftware.com). You can enter a route specification like this:

From ORD:: UA UA UA+
To FAT:: UA UA UA+

Which will only find flights with three or more segments on UA. You can also search multiple airports at a time, but I find it works better with only one airport. Describing the full route language would also take a long post, but you should be able to find more info searching, and in the Mileage Run Deals forum stickies.