I intend to have a ?Distance Measuring Sensor? placed on top of, and connected to a screen showing a video. As a viewer moves closer to the sensor and to the screen, they will have an effect on the video. 

The distance of the viewer to the sensor will be relative to the change in the video. For instance, as the viewer retreats from the sensor, the video will move back towards its original point, but if the sensor senses something nearing, then the opposite will happen.

I have been looking at the Sharp GP2D12 sensor, which I would want to connect via USB to my computer.

I would need the sensor input to trigger my video, and was wondering if anyone could provide an insight into how I might go about achieving this. I am completely new to MaxMSP, but have computer technicians available at my University to help me figure it out (hopefully).

I intend to have a ?Distance Measuring Sensor? placed on top of, and connected to a screen showing a video. As a viewer moves closer to the sensor and to the screen, they will have an effect on the video. 
The distance of the viewer to the sensor will be relative to the change in the video. For instance, as the viewer retreats from the sensor, the video will move back towards its original point, but if the sensor senses something nearing, then the opposite will happen.

video-project-with-sharp-ir-distance-detector

I've used many of these sensors without problems.

1) You need some way to get the analog voltage into your computer, and Max. There's a thread going about sensors that lists a noumber of possibilities.

https://cycling74.com/forums/index.php?t=msg&th=17900

 &start=0&rid=2634&S=4a06a49e8f69a7cd813d32d21cf6 63c3

2) You should look at the Jitter Tutorials regarding playback of video.

3) Once you got those two things together, it becomes a matter of translating the incoming numbers from your sensor interface into the right "play the video" message. Somebody just asked this same question, except their sensor was a dance floor, rather than a range sensor.

https://cycling74.com/forums/index.php?t=msg&goto=612

 03&rid=2634&S=4a06a49e8f69a7cd813d32d21cf663c3#msg_6 1203

Feel free to post more questions once you've combed through some of this material.

1) You need some way to get the analog voltage into your computer, and Max.  There's a thread going about sensors that lists a noumber of possibilities.

 https://cycling74.com/forums/index.php?t=msg&th=17900 &start=0&rid=2634&S=4a06a49e8f69a7cd813d32d21cf6 63c3

3) Once you got those two things together, it becomes a matter of translating the incoming numbers from your sensor interface into the right "play the video" message.  Somebody just asked this same question, except their sensor was a dance floor, rather than a range sensor.

 https://cycling74.com/forums/index.php?t=msg&goto=612 03&rid=2634&S=4a06a49e8f69a7cd813d32d21cf663c3#msg_6 1203

An easy way to get the GP2D12 data into Max is with Teleo from Making Things.

Video Project with Sharp IR Distance Detector