Cita:
Iniciado por IsaBelM 
es lo mismo que tienes hasta ahora, pero agregando delante tanto parentNode como sea necesario
lee esto ¿Te refieres a lo siguiente?
Código HTML:
<form method="post" action="#">
<table>
<tr onchange="this.parentNode.parentNode.nextSibling.nextSibling.style.display='block'">
<td>
<select name="select1.1">
<option value=""></option>
<option value="select1.1Option1">1</option>
<option value="select1.1Option2">2</option>
<option value="select1.1Option3">3</option>
</select>
</td>
<td>
<select name="select1.2">
<option value=""></option>
<option value="select1.2Option1">1</option>
<option value="select1.2Option2">2</option>
<option value="select1.2Option3">3</option>
</select>
</td>
</tr>
<tr onchange="this.parentNode.parentNode.nextSibling.nextSibling.style.display='block'" style="display: none">
<td>
<select name="select2.1">
<option value=""></option>
<option value="select2.1Option1">1</option>
<option value="select2.1Option2">2</option>
<option value="select2.1Option3">3</option>
</select>
</td>
<td>
<select name="select2.2">
<option value=""></option>
<option value="select2.2Option1">1</option>
<option value="select2.2Option2">2</option>
<option value="select2.2Option3">3</option>
</select>
</td>
</tr>
</table>
</form>