I'm going to try employ the mechanism which I used before: Using the keys on your keyboard to play an image and combine it with Playing a video in Gem. 
So basically what I need to do is to create four separate render chains for each of my movies.
To do so I need a 'pix_film' object to texture my video file to my shape. I need to tell 'pix_film' which movie I want to open and I can do it by using 'bang' and 'openpanel' which will open the the browser and let me pick the movie I want to use. Message box holds one or more message and every time the 'message box' receives any message it will be sent to the destination. I'm going to use '$1' message to make my message variable and to accept and open the file name that I will give. I'm going to use a QuickTime file as it works better on Mac. To tell pd to start to play my movie I need to give it an 'auto $1' message and link it to the 'pix_film'. My message needs also a 'toggle' to turn it on and off.    
I'm going to use the patch I created before.

Then I'm going to add to my patch the 'key object', a 'number box' and four 'select object' boxes with numbers so each time I press the letter 'a', 'b', 'c' or 'd' different movie file will play. 
The 'key object' reports the numbers of 'printing' keys of the keyboard. Other words the 'key object' will output a specific number to a number box each time I press the key on my keyboard. 
The 'select object' compare numbers or symbols and checks its input against the constant '0 message' in case of my patch. If they match, the first outlet gives 'bang'. To play a different movie each time I press different key ('a', 'b', 'c' or 'd'). I need to add four '0 messages' and join them through the inlet to each 'select object' assigned to one movie render chain and through the outlet to the other three render chains through their 'toggle'. This way pd will send the message to play one movie and stop playing the three others.
This is my patch.