You mentioned timecode, which indicates to me you know the part in the video where the light should be triggered. If you know that, you could sync a countdown in the arduino with the video start.
Could be as simple as 'pushing two buttons at the same time', but if you're using Max then you could get it to trigger (via serial) the countdown on the arduino (one button now not two! but your laptop is required).
Alternatively, and perhaps for fun is to use (coded sequences of) single frame flashes in the video (or find appropriate triggers in the video itself) to trigger light sensors which in turn trigger the light, or a countdown to the light. This way the arduino/light could be separate from the video system, i.e. no more laptop - assuming there is some other video playback device present.
The arduino to relay 110V switching part is the easiest, and I'm guessing there will be lots of tutorials and circuit diagrams online.