Table question

[uber]

Right, I have a table with a green content box in the middle, and then at either side of the content box i have a black box about 70 px wide.
The table expands as content is added, and I am using valign="top".
I have set all 3 cells to height="100%" but it still doesn't do what I want them to do.
I want the table to go right to the bottom of the page if the content doesn't go right down.

Here is a screenshot of my page in firefox:
http://www.****************/uploads/fc537169e6.png

[Colin-Roberts]

</br> </br> would make it expand to the bottom but thats not the proper way to do it.