I believe it's still a nested ticket even though its two different places.

http://www.nolo.com/lawstore/product...ampleChapter/4

The key is the airline sees you on _two_ itineraries at once. However, since your second itinerary doesn't go all the way back home you probably wouldn't raise any flags, since there are real reasons to have nested tickets (for example, I live in PIT, fly to WAS for two weeks, and see a nice e-saver to RDU while I'm there. So instead of staying in WAS for the weekend I go to RDU an get back.)

To be safe in these situations, your best bet is to simply fly two different airlines. As per being able to buy it on the website, if that argument flies for you good luck. I wouldn't risk it myself.