[TowerTalk] Budget 4-Pack?

[Barry Fox]

I have two HF radios and 4 different HF antennas.  I would like to use
each rig on any antenna, while obviously locking out that antenna for
the other rig.  The commercial products 6-Pack, 8-Pack, etc are way
over my budget.  Anyone have a schematic for a "4-Pack" or similar
device they would like to share?  Obviously relays are the way to
go, and I can get the RF relay switching part of it on paper but 
not the lockout logic.  Some sort of electro-mechanical exclusive-OR 
gate array / diode matrix?  Anyone been there and done that?
TNX / 73,
Barry - W1HFN