no problem,

An empty excel xml file will be something like this, I'd edit this by adding styles I'd need for my report and perhaps even the header of my report and have this saved as a template text file to load in.

<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
 xmlns:o="urn:schemas-microsoft-com:office:office"
 xmlns:x="urn:schemas-microsoft-com:office:excel"
 xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet">
 <DocumentProperties xmlns="urn:schemas-microsoft-com:office:office">
  <Version>10.2625</Version>
 </DocumentProperties>
 <OfficeDocumentSettings xmlns="urn:schemas-microsoft-com:office:office">
 </OfficeDocumentSettings>
 <ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel">
  <WindowHeight>9000</WindowHeight>
  <WindowWidth>13860</WindowWidth>
  <WindowTopX>240</WindowTopX>
  <WindowTopY>75</WindowTopY>
  <ProtectStructure>False</ProtectStructure>
  <ProtectWindows>False</ProtectWindows>
 </ExcelWorkbook>
 <Styles>
  <Style ss:ID="Default" ss:Name="Normal">
   <Font ss:FontName="Arial1" ss:Size="10"/>
  </Style>
 </Styles>

 <Worksheet ss:Name="Sheet1">
 </Worksheet>

</Workbook>

I'd then read this in line by line til I go to the start of the worksheet and add my content.

   <Table ss:DefaultColumnWidth="50" ss:DefaultRowHeight="15.75">
    <Column ss:Width="100"/>
    <Column ss:Width="100"/>
    <Row ss:Height="15.75">
     <Cell ss:StyleID="Default"><Data ss:Type="String">This is my test sheet</Data></Cell>
     <Cell ss:StyleID="Default"><Data ss:Type="Number">1234567890</Data></Cell>
    </Row>
   </Table>

save that textfile as yournewxslfile.xsl and you should have a working excel file without touching automation.

so my code in fox for adding a new row to that looks like this

tstring1 = fgets(templatefile,1000)
do while alltrim(tstring1) != "</Table>"		
 fputs(newxlsfile,tstring1) && Write string into file
 tstring1 = fgets(templatefile,1000)					
enddo	
							
tstring =  '<Row ss:Height="15.75">'
fputs(newxlsfile,tstring) && Write string into file	
tstring =  '<Cell ss:StyleID="Default"><Data ss:Type="String">' + alltrim(mystring_variable) + '</Data></Cell>'
fputs(newxlsfile,tstring) && Write string into file
tstring =  '<Cell ss:StyleID="Default"><Data ss:Type="Number">' + alltrim(mynumber_variable) + '</Data></Cell>'
tstring =  '</Row>'
fputs(newxlsfile,tstring) && Write string into file
tstring =  '</Table>'
fputs(newxlsfile,tstring) && Write string into file
tstring =  ' </Worksheet>'
fputs(newxlsfile,tstring) && Write string into file
tstring =  '</Workbook>'
fputs(newxlsfile,tstring) && Write string into file

pretty much everything is available right down to conditional formatting and the like.

I suggest creating very simple spreadsheets in excel that contail just the style or effect you want to apply and then in excel saveas xml, open the file in a text editor and you should be able to work out quite easily how to do it.

also the full helpfiles for the office xml formats are available from microsoft here
http://www.microsoft.com/downloads/details.aspx?FamilyId=FE118952-3547-420A-A412-00A2662442D9&displaylang=en

Hope that helps.