Two ways come to mind:
1. You can use AT commands from the computer to change the settings on the Programmer XBee and change the DLID to match the MYID of the particular Fio XBee you want to talk to at that time. The drawback is that you have to have a gap before you send +++ and a gap afterward, and then you send ATDL 000x(enter) and then ATCN (enter) where 000x is the ID you want to talk to. The XBee allows these gaps to be changed, speeding up the process.
2. You can change your Programmer XBee into "API Mode" and use the Arduino XBee API library (try this one, but there are probably others: https://code.google.com/p/xbee-arduino/
) and you can change the DL address with every packet.
Hope that helps
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