Javascript+HTA, reload iframe and keep scroll position

I created an account a very long time ago but I never really use it, as I always manage to find the answers to my questions in already solved threads. So, this is the first time since I'm working on my current program that I was not able to find a working answer on SO. However, if I simply missed it, please be nice to me ^^

A bit of context that may explain why I can't manage to apply any given solution despite many threads exists about this... I am doing:

A HTA Interface
With an iframe to a local text file
And a link to a js file that I want to use to refresh the iframe every 500 ms.

The goal is to make a chat; people can write on the text file and it automatically appears on the HTA interface.

I don't know ANYTHING about JS, frankly. So I found here that piece of code to refresh the iframe.

window.setInterval(function() {
    document.getElementById('chatbox').contentWindow.location.reload();
}, 500);

It works, but upon refreshing the iframe, it scrolls back to the top; which makes the chat unreadable, as you can guess. Many solutions that I've read on SO won't work for me, maybe because it doesn't fit with this way of refreshing iframes, or with HTA, or I'm just too dumb with js to know how to make them work.

If anyone has a solution that I could just copy and use, even if I don't understand what I'm doing - it won't be very satisfying intellectually but at least I could focus on finishing my interface :) thanks a lot!

Solution

If you refresh the iframe by updating innerHTML from the text file, instead of doing a reload, it won't change the scroll position. Here's an example HTA:

<!DOCTYPE html>
<meta http-equiv="x-ua-compatible" content="ie=9">
<html>
<head>
<script>    
function Refresh() {
  var Iframe = document.getElementById("chatbox").contentWindow;
  window.setInterval(function() {
    var fso = new ActiveXObject("Scripting.FileSystemObject");
    var fh = fso.OpenTextFile(".\\Chat.txt",1);
    var FileContents = fh.AtEndOfStream ? "" : fh.ReadAll();
    fh.Close();
    Iframe.document.body.innerHTML = "<pre>" + FileContents + "</pre>"
  }, 500);
}
</script>
<style>
#chatbox {height:30em;}
</style>
</head>
<body onload="Refresh()">
  <iframe id=chatbox title="Chat Box">
</iframe>
</body>
</html>