mauried:
Alternatively another way to do this is to have accurate clocks in each box and when the button is pressed, the time it was pressed is sent to the receiver.
This way , the actual time it takes for the transmissions to be received is not relevant any more, but you then
Radio transmissions are never going to be 100% reliable, some 'button presses' will not be received. Therefore there needs to be a send and acknowledge protocol, to ensure button presses are not missed due to interference.
The only way I can see a send and acknowledge system being reliable, is if you know exactly when (in absolute time) each button was pressed.