Official comment
The RB-DMX1 is getting the lighting phrases and sending the information out to the lights you have numbered in the universe. It will only work from one source, doing a back to back would be tough since you would need a second box and you'd have to switch the DMX out cable each time from laptop to laptop. Another thought would be to have you switch the USB cable each time and then it would run off the other DJs light show if they had the same fixtures set up in the DMX universe.