Will do, thx.  I've got an old beater laptop I could try it with if I can figure out a good way to mount it in the cab and be able to take it out easily every night.  Too many crackheads around to leave attractive stuff in the cab.  I'll demo the farmergps program and see if I can get it to do something like an EZ500 with EZBoom (see below).  It wouldn't be that expensive an upgrade if I used it with my existing EZG+ output though. 

 Oh, for others who're interested, my local EZGuide salesman (Will at atlanticprecision.ca- thanks Will!) emailed me privately and said that an EZ500 system with EZBoom will do basically what I want now.  I'd just have to define a 200' boom with two sections, left and right.  When I'm spraying left, turn on the left section, etc.  I assume I'd have to have two pairs of chemical solenoids to "fake" the two sections with upper and lower cannons.  Actually, now that I think on it some more, this would allow me to define the coverage for the upper and lower cannons if I made 4 sections for the EZBoom (upper and lower left, upper and lower right).  Very nice, and I could probably even define a 5th section for the dead spot under the tractor that doesn't get sprayed and leave it turned off all the time. 

 Trouble is I'm cheap and it could be done adequately with just software.  An EZ500 + EZBoom isn't terribly cheap, but it would be very nice, and I want a second system anyway...