value of text boxed within table tr should not contain same value

if i have
<table id=tbl>
<tr>
<td>
<input type=text name=nm1>
</td>
</tr>
<tr>
<td>
<input type=text name=nm2>
</td>
</tr>
<tr>
<td>
<input type=text name=nm3>
</td>

</tr>
</table>