I'm not sitting in front of the game at the moment, but if you go in to the config menu, there will be three buttons to configure movement, commands, and (something else).
If you go in to the commands, you will see a long list of key bindings. The ones you want say (I think) Cursor Move Up and Cursor Move Down... Something like that. ^-^;
Assign one key to each (I have 'z' for up and 'x' for down). Then, if you target yourself and hit your new up key (z), it will target the last member of the second party in the alliance. Hitting it again will take you to the next-to-last member. Going the other way, from you, down will target the second person in your party, then the third, etc. Yes, it wraps, so if you go down from the last member of your party, it will jump up to the first member of the first alliance party (or second if only 2 parties, or to you if there's no alliance.)
If no one else gives the specifics, I'll edit this post when I am sitting in front of the menu and not working on (a poor) memory alone. ^-^;