I'm not sure which of these examples is what you want. Your description seemed to be the opposite of your drawing, but try these out.

<div style="width:250px;padding:10px; border-left: solid black 1px;border-right: solid black 1px;">
<table width="100%" style="border-top: solid black 1px;border-bottom: solid black 1px;">
<tr>
<td>cell 1:1</td>
<td>cell 1:2</td>
<td>cell 1:3</td>
<tr>
<tr>
<td>cell 2:1</td>
<td>cell 2:2</td>
<td>cell 2:3</td>
<tr>
</table>
</div>
<br /><br />
<div style="width:250px;padding:10px; border-top: solid black 1px;border-bottom: solid black 1px;">
<table width="100%" style="border-left: solid black 1px;border-right: solid black 1px;">
<tr>
<td>cell 1:1</td>
<td>cell 1:2</td>
<td>cell 1:3</td>
<tr>
<tr>
<td>cell 2:1</td>
<td>cell 2:2</td>
<td>cell 2:3</td>
<tr>
</table>
</div>