Video Processing problem with saving the AVI afterconverting it from an array

Hi,

I'm new to MATLAB and i need some help. so far i have made an AVI background remover by using Z-stack for the series of images in the AVI and the function looks like this:

 C = {'Moviessmall.avi';'Moviessmall_2.avi';'Moviessmall3.avi'};
 for ii = 1:length(C) 
  Vid1 = VideoReader(C{ii}) 
  Vid1Frames = read(Vid1)
  Vid2Frames = rgb2gray(Vid1Frames);
  Vid3Frames = Vid1Frames(:,:,1:450);
  VidB = median(Vid3Frames, 3);
  VidB2 = repmatrepmat(VidB, [1 1 450]);
  Vid2 = Vid3Frames-VidB2;

the final step of the function it to subtract two arrays to get the final produce but i wanted an AVI at the end and not an array. also i would like to know how to then save the AVI into a Folder after the array has been converted to an AVI. If anyone can point me to the right direction that would help alot.

Thank you,

Minh