It sadly isn't possible in Gnutella in general.
As explanation: The strings you enter are being sent directly into the network and other clients decide how to react to them.
Since Phex isn't the only Program in the Gnutella Network, it isn't easy to change the way searches are conducted (especially because gnutella programs have quite advanced methods of managing incoming searches, which would need to be completely redesigned).
But there have been ideas to make more complex searches possible for some time now, so if you want these searches, talk to other Gnutella users, organize them and talk to the programmers of several clients at the same time (means: Just write friendly feature requests and follow up on questions about them).
If you then repost in here, I can post your request in the Gnutella Development Forum, so it can be discussed between the developers again.
As condition for this to have a chance of success, you'll need at least 10 users, who also see "getting advanced searches" as their priority, and you need to have at least one user of every big client:
- LimeWire
- Phex (OK, you're here already
)
- gtk-gnutella
- Shareaza (even though they didn't do that much for Gnutella for some time) - they have their own Forum.
If all programmers got these requests and see that many users want complex searches, the chances of them being implemented rise greatly.
The best wishes,
Arne