XBee Synchronization
That is the solution, something like timestamp. Since I need to send unicast messages to all the modules and since I know all the MAC addresses in order, from MAC 1 to MAC 64, what I do is add a byte to my message with the delay so the PIC18 can wait until it executes the command. So 1 transmission takes around 10ms, 64 transmissions take 640ms. Knowing this the MAC 1 receives 640ms of delay MAC 32 receives 320ms delay and MAC 64 receives 0ms delay. By doing this I can have a kind synchronization. The only problem are the hops, because if I have many hops the delay wont be 10ms, but that is not a problem to me.