Help on Matrix falling rain code

Hey guys so I got into my head to try to recreate the the falling rain effect from the Matrix movies in Matlab.

Here's what I've got so far

clear all
close all
clc

cmdWinDoc = com.mathworks.mde.cmdwin.CmdWinDocument.getInstance;
listeners = cmdWinDoc.getDocumentListeners;
for i = 3:4
    jTextArea = listeners(i);
    jTextArea.setBackground(java.awt.Color.black);
    jTextArea.setBackground(java.awt.Color(0,0,0));
    set(jTextArea,'Background','black');
    set(jTextArea,'Background',[0,0,0]);
    jTextArea.setForeground(java.awt.Color.green);
    jTextArea.setForeground(java.awt.Color(0,1,0));
    set(jTextArea,'Foreground','green');
    set(jTextArea,'Foreground',[0,1,0]);
end

for j = 1:10000
  A9=['A':'Z' '0':'9' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ';];
  Data=zeros(length(A9),105);
  for k=1:size(Data,2)
      Data(:,k)=randperm(length(A9));
  end
  Data=A9(Data)
end

for i = 3:4
    jTextArea = listeners(i);
    jTextArea.setBackground(java.awt.Color.white);
    jTextArea.setBackground(java.awt.Color(1,1,1));
    set(jTextArea,'Background','white');
    set(jTextArea,'Background',[1,1,1]);
    jTextArea.setForeground(java.awt.Color.black);
    jTextArea.setForeground(java.awt.Color(0,0,0));
    set(jTextArea,'Foreground','black');
    set(jTextArea,'Foreground',[0,0,0]);
end
clc

I would want to change that central for-loop to a while-loop, but I was having issues trying to figure out how to leave the while loop with a keypress.

I'm wondering if anyone has any better ideas for how to achieve this falling rain effect as right now this code more spams random letters than having them rain.