Getting Content Of A Textarea With AJAX

I'm trying to achieve something that I originally thought would be very simple, but I can't get it working....and even googling hasn't helped this time! All I want to do is update the innerHTML of a div with the content of a textarea object when a button is clicked. I'm trying to avoid having to post the form using AJAX because the button also replaces the innerHTML of a different div with the value of a text input box. Here is the code I've tried, but it doesn't work:

Code:

function previewContent(intContentId) {
var titleText = document.getElementById('edit_title_' + intContentId);
var titleDiv = document.getElementById('content_title_' + intContentId);

[Code]....

In this example, the titleText var represents the text input box, and the contentText var is the textarea. The titleDiv gets correctly updated with the current value of the input box, but the contentDiv doesn't seem to consider any changes I make within the textarea - it just loads the original content. This seems very strange to me. Is there an easy way to retrieve the value of the textarea?