Problems building 'ultimate' scrolling table

Originally posted this one in the CSS forum, with no results, hopefully I'll have better luck here...




I am trying to build a table in which the center scrolls both ways but the columns and rows around the edges stay put - have a look at the page below using IE6 to see what I mean:

www .hilarybarry .net/james/test2 .html

This is working exactly as I want it to in IE6, my problem is that I can't get it to work right in IE7 - the horizontal scrolling is not working properly.
By re-instating the commented out code on line 81 I can get it to sort of work, but I don't want to have to specify the width like this as the table contents are going to be dynamic and there is no way of knowing how wide they will be.

This is for use on a company intranet where all the users have IE6 or IE7, hence I am not concerned with other browsers or earlier versions of IE.

Any help getting this working would be much appreciated...

P