Resize DIV to fit parent and have scroolbar, using CSS

[CVMichael]

I'm working on a ASP.NET app, but the issue is mainly with CSS

I have a table with 2 cells, and I want to have a scrollbar in he second cell

Something like:

<Table>
<tr>
   <td>
      1<br />
      2<br />
      3<br />
   </td>
   <td style="height: 100%; width: 400px;">
       <div style="overflow: auto;">
          1<br />
          2<br />
          3<br />
          4<br />
          5<br />
          6<br />
          7<br />
          8<br />
          9<br />
          10<br />
          11<br />
          12<br />
       </div>
   </td>
</tr>
</Table>

So I want the second cell to have the height of the first cell (the 3 items), and have a scrollbar to scroll up/down the 12 items.

I can't set a fixed height because the size of the first cell changes depending on content inside.