you should probably find out the length of the first movie   http://processing.org/reference/libraries/video/Movie_duration_.html then compare it with how much time has elapsed since the first movie started playing, when those values match (or whatever relevent condition that you determine is met) start playing the next video. I'd suggest just testing this with two of the video's before moving on to include a third one. This can be achieved with a conditional. here's a helpful thread on setting up a timer in processing  http://forum.processing.org/topic/timer-in-processing Also worth noting that if you are not fammiliar with using conditionals the processing reference and ascociated link on that page are good resources to help you get started  http://processing.org/reference/if.html

An Introduction to Programming with Processing
http://www.processing.lyndondaniels.com

2. import processing.video.*;
3. Movie video1, video2, video3;
4. 
   
5. boolean playVideo1 = true;
6. boolean playVideo2 = false;
7. boolean playVideo3 = false;
8. 
   
9. 
   
10. void setup() {
11.   
12.   size(500, 500);
13. 
    
14.   video1 = new Movie(this, "video1.mov");
15.   video2 = new Movie(this, "video2.mov");
16.   video3 = new Movie(this, "video3.mov");
17. }
18. 
    
19. 
    
20. void draw() {
21. 
    
22.   if (playVideo1 == true) {
23.     video1.play();
24.     image(video1, 0, 0);
25.     //println(video1.time() + "\t" + video1.duration());   
26.     if (video1.time() + .03 >= video1.duration()) {
27.       video1.stop();
28.       playVideo1 = false;
29.       playVideo2 = true;
30.     }
31.   }
32. 
    
33.   if (playVideo2 == true) {
34.     video2.play();
35.     image(video2, 0, 0);
36.     //println(video2.time() + "\t" + video2.duration());    
37.     if (video2.time() + .03 >= video2.duration()) {
38.       video2.stop();
39.       playVideo2 = false;
40.       playVideo3 = true;
41.     }
42.   }
43. 
    
44.   if (playVideo3 == true) { 
45.     video3.play();
46.     image(video3, 0, 0);
47.     println(video3.time() + "\t" + video3.duration());     
48.     if (video3.time() + .03 >= video3.duration()) {
49.       video3.stop();
50.       playVideo3 = false;
51.       playVideo1 = true;
52.     }
53.   }
54. }
55. 
    
56. 
    
57. void movieEvent(Movie m) {
58.   m.read();
59. }

http://code.google.com/p/simple-cinema/