appending frames to an existing .avi file

am trying to figure out a way to append frames to .avi files.

In a simplistic way I want to:

open and set up multiple movie files, close it and then reopen and add more video frames to it.

 for i=1:n1
     open the moviefile(i) using: 
              myVideo(i) = VideoWriter (name, option)
              open(myVideo(i))
     write a title screen to moviefile(i) using:
              writeVideo (myVideo(i), plotID)
     close moviefile(i) using:
              close (myVideo(i))
   end
then:
   for j = 1:n2
      read n1 datastreams from file(j)
      process data from file(j) into n1 different plots 
      for i=1:n1
          open myVideo(i)
          append plot(i) to myVideo(i)
          close myVideo(i)
      end
   end

It sounds simple, but the second loop on "i" does not work. I can open myVideo(i), but when I write to it, the previous contents are overwritten. I cannot see an option "append" to writeVideo, so I presume there must be some other workaround and/or a different way (other than VideoWriter) to start the whole process. Any help/suggestion will be appreciated.

disclaimer: I have seen the existing answers to a similar question, and neither fit my case because: option 1): I cannot keep all the .avi files continuously open (run out of memory) option 2): only applies to windows machines (I am working on a OSX platform)

[Carl Witthoft]

According to other threads, WriteVideo will not append. There's a thing on FEX called "mmwrite," Windows only, requires DirectX9, that might work. MathWorks is being overly cautious again (since appending mismatched image frame types would be really bad).