Someone

<table>
<tr><td>t0</td><td>text</td><td>&nbsp;</td><td>v?</td><td>text</td></tr>
<tr><td>t1</td><td>something</td><td>something</td><td></td><td> v? v-1</td></tr>
..
..
..
</table>

I need to replace v? with the text in the first column for that row ie (t0,t1...)
and v-1 with the text in the column before (in this example it should be t0) 

To replace the v? in a row, do this:
  regsub {(<tr><td>(.*?)</td>.*)v\?} $row {\1\2} updatedRow