Ok, so assuming you have an HTML structure something like this:
<table width="90%">
<tr>
<td>
<div class="greybox" style="margin-top:2%;">
<table class="datagrid" width="100%">
<tr>
<td>UniqueText</td>
</tr>
</table>
</div>
</td>
</tr>
</table>
...and as per your current solution you can rely on "UniqueText" being present, then you could try the following XPath statement:
(//table[contains(., 'UniqueText')])[last()]
So in QTP/UFT you'd be doing:
Browser("micClass:=Browser").Page("micClass:=Page").WebTable("xpath:=(//table[contains(., 'UniqueText')])[last()]")