zen region to right of content and below highlighted

I've created a sub theme with a region called "content-right" and I'm attempting to place it to the right of the content region below the highlighted region (see attached image).

My problem is that no matter where I place the "render($page['content_right']);" code, and regardless of what I do to the CSS, I can't seem to get the content-right region to position itself to the right of the content region.

I concocted the following scheme by editing page.tpl.php and adding some CSS, but I'm afraid it's not much more than a kludge. What I did is to first determine if the content-right content exists. If so, I add a div with a CSS class that shrinks the content region so the content-right region will fit. If content-right doesn't exist, then content extends to the right border:

	  <?php $content = render($page['content']); ?>
	  
	  <?php $content_right = render($page['content_right']); ?>
	  
	  <?php if ($content_right): ?>
      <div class="content-collapse"><?php print $content; ?></div>
	  <?php print $content_right; ?>
	  <?php else: ?>
	  <?php print $content; ?>
	  <?php endif; ?>

I'm sure there is a more elegant and correct way to render this. I'm looking for suggestions on a better way to implement this. Thanks.