short answer is No. There is no direct way to disable the back button so that it is greyed-out and user cannot click on it. However, there are some tricks using javascript which might be able to give you the results you need,although they won't be as pretty. One I am currently working on involves using javascripts window.history function with a session variable and automatically logging off and redirecting to login page if user hits the back button. You can also do something as simple as:
<script language="JavaScript">
<!--
javascript:window.history.forward(1);
//-->
</script>
Put that script at the top of every page. If user hits back button it will send them forward again.