OK, I've done a bit more digging on this. Apparently, you need to put a DIV inside your table, and then the DIV generates the scrollbars.
Something like this:
Code:
<table border="1">
<tr>
<td>Here is some text in the main table
<table border="1">
<tr>
<td><div style="width: 200px; height: 200px; overflow: scroll;">
<p>This is the table-within-a-table</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
<p>Text</p>
</div>
</td>
</tr>
</table>
</td>
</tr>
</table>