HTML <td> rowspan at the end of a table

[JnrJnr]

Hi, I have a table that has, say 3 rows and two columns in each. I need to create a rowspan for the third column on the last <td>.
Is it possible to create a rowspan for an HTML table when rowspan is created at the last <td> in the table?
Like this:

<table width="100" border="1" cellspacing="3">
  <tr>
    <td>dd</td>
    <td>dd</td>
  </tr>
  <tr>
    <td>dd</td>
    <td>dd</td>
  </tr>
  <tr>
    <td>dd</td>
    <td>dd</td><td rowspan="3" valign="top">ss</td>
  </tr>
</table>

It seems like it only works when you place rowspan at the first <td> in the table.
Any ideas? I want to do it like this for a dynamically created table in PHP.

[Dormilich]

a rowspan in the last row will never work out (because there are no more rows to span over)