namespaces in xml generated by excel

Hi everyone!
After save some excel document in xml format, I'm trying to apply some xsl to make a result xml file just with a small part of the original.
The original is something like this:

<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-comffice:spreadsheet"
xmlns="urn:schemas-microsoft-comfficeffice"
xmlns:x="urn:schemas-microsoft-comffice:excel"
xmlns:ss="urn:schemas-microsoft-comffice:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<DocumentProperties>...</DocumentProperties>
<Styles>...</Styles>
<Worksheet ss:type>
<Table ss:ExpandedColumnCount="7" ss:ExpandedRowCount="17" x:FullColumns="1"
x:FullRows="1">
<Column ss:Index="2" ss:Width="75"/>
<Column ss:Width="54"/>
<Row ss:Index="5">
<Cell ss:Index="2"><Data ss:Type="String">Segunda</Data><NamedCell
ss:Name="Agenda"/></Cell>
...
...
</Worksheet ss:type>
<Worksheet ss:type>...</Worksheet ss:type>

How can I do a XSL file to match just the Cells that have a NameCell attribute value like Agenda?!

Many thanks!!