Selecting a particular node of an XML generated from

Hello,

I have a requirement where I am not sure of the best possible
solution. The XML is generated from Excel. The problem is with missing rows
which makes it difficult to select a particular node. Better I explain using
this sample XML: [Pls ignore any case mismatch or spell mistakes]

<root>
   
<Row>
        <Cell><Data>u1</Data></Cell>
        <Cell><Data>13.7 billion
years ago</Data></Cell>
        <Cell><Data>Hydrogen and helium nuclei form in
the first three minutes...</Data></Cell>
        <Cell
ss:Index="107"><Data>107</Data></Cell>
        <Cell><Data>108</Data></Cell>
        <Cell><Data>109</Data></Cell>
        <Cell
ss:Index="115"><Data>115</Data></Cell>
        <Cell><Data>116</Data></Cell>
        <Cell><Data>YES</Data></Cell> <!-- this is 117th row. But position()
!= 117  -->
        <Cell><Data>118</Data></Cell>
    </Row>
    <Row>
       
<Cell><Data>u2</Data></Cell>
        <Cell><Data>2 million
yearsgo</Data></Cell>
        <Cell><Data>blahlah</Data></Cell>
       
<Cell><Data>1</Data></Cell>
        <Cell><Data>2</Data></Cell>
        <!--
SO MANY ROWS HERE -->
        <Cell><Data>YES</Data></Cell>   <!-- THIS IS
117th row (Cell) i.e. position() = 117 -->
        <!--GAIN SO MANY ROWS HERE
-->
        <Cell><Data>199</Data></Cell>
       
<Cell><Data>200</Data></Cell>  <!--ASSUME THIS IS 200TH ROW -->       
   
</Row>
    <Row>
        <Cell><Data>u3</Data></Cell>
       <Cell><Data>20th
century</Data></Cell>
        <Cell><Data>blah blah</Data></Cell>
       
<Cell ss:Index="117"><Data>NO</Data></Cell>   <!-- THIS IS 117th row But
position() != 117  -->
        <Cell ss:Index="199"><Data>119</Data></Cell>
    </Row>   
</root>


The excel to xml convertion results in empty excel
columns getting stripped out in the resulting <Cell>. And so, the number of
<Cell>'s vary for each <Row>. Now, if I want to select a particular <Cell>,
say 117th <Cell>, I need to check any @ss:Index exist and if so, count()  the
number of the preceding-sibling's + the preceding @ss:Index value. So, for
117th Cell value, 


(A) in Row 1, 2nd <Cell> of @ss:Indiex is 117th
(B) in
Row 2, position() = 117 is the required one
(C) in Row 3, @ss:Indiex matching
117
(D) if none matching found, ignore


In my requirement, I need to select
the N-th <Cell> value and check whether it is 'yes' or 'no' and then process.
I am trying approach something like this (incomplete)



<xsl:for-each
select="Cell">
  ...

  <xsl:variable name="last-index "
select="preceding-sibling::Cell[@ss:Index][1]"/>  

 <!-- the ABOVE giver the
last <Cell>'s ss:Index value.

Now I need to do something like
count(preceding-sibling::Cell[@ss:Index][1]) - this may be wrong, but here is
what I having trouble and need suggestions and best approach to solve this, to
select N-th <Cell>, where N is known and can be 1 to X (=max possible value).
Thanks in advance!. 



Regards,
karl