put an Iframe in the middle column and give it a NAME.
Then with some god awful javascript, maybe something like this:
<script>
function change(page){
url = page;
//my IFRAME is called Biosonik
parent.frames['biosonik'].location.href = url;
}
</script>
then on your menu just put: OnClick="javascript:change("mypage.php")"
...its something like that, you could probably use targets instead but thats to easy, easy is boring.