no i can't think of any way you could do this with a UX2 with the default setup.  the headphone and all the outputs are all taken from the same source I think.  you could try using ASIO4ALL drivers, and then use another sound card for your other headphone output, but that's not supported by line6, so if you can't get it to work, then that's it.

that said, just because I don't know doesn't mean that's 100% certain.

you could check out the pod famr manual here: http://line6.com/support/manuals/ and see what it says.  if you can do it, it'll be in there.