Select input field according to TH and TR - xpath

Question

I have a next table with TH:
<table cellspacing="1" border="1" id="FinancialsGrid">
<thead>
<tr>
<th>Product</th>
<th>Slice</th>
<th>Units</th>
<th>Accrual Rate</th>
<th>Trend Factor</th>
<th>Base Units</th>
</tr>
</thead>
<tbody>
<tr>
<td rowspan="3">Lorem Ipsum</td>
<td>Previous</td>
<td>6,866</td>
<td>0.00 %</td>
<td>0.00 %</td>
<td>6,866</td>
</tr>
<tr>
<td>Current</td>
<td>6,866</td>
<td>0.00 %</td>
<td>0.00 %</td>
<td>6,866</td>
</tr>
<tr>
<td>Proposed</td>
<td>6,866</td>
<td><input type="text" style="width:60px;" value="0.00 %"></td>
<td style="width:60px;"><input type="text" style="width:60px;" value="0.00 %"></td>
<td style="width:60px;"><input type="text" style="width:90px;" value="6,866"></td>
</tr>
</tbody>
</table>
I need to select an xpath for input field according to e.g. "Trend Factor" column.
My variant which I wrote doesn't work:
//table[#id='FinancialsGrid']/tbody/tr/td/input[count(//table/thead/tr/th[.='Trend Factor'])]
Table view:

Answer 1

Here is the XPath
(//table[#id='FinancialsGrid']//input)[count(//tr/th)-index-of(//tr/th, //tr/th[text()='Trend Factor']) + 1]
or another one without index-of() function (for Firebug):
(//table[#id='FinancialsGrid']//input)[count(//tr/th)-count(//tr/th[text()='Trend Factor']/preceding-sibling::*)]
Will grab required input node, where:
count(//tr/th) is count of columns
index-of(//tr/th, //tr/th[text()='Trend Factor']) - current number of column
(//table[#id='FinancialsGrid']//input) - sequence of input nodes.
So we calculating position of input node and grubbing node from sequence.