Are you outputting Excel code? or is it XML or ...?
If its the actual excel code your best bet is to ask a group like the OpenOffice.org (http://www.openoffice.org/) group (they make an Open Source Microsoft Office replacement, including Excel) or another opensource group dealing with Office.
Re: Putting header and footer info in an Excel spreadsheet generated using Response obj
I'm not sure which method your using, the urn:schemas-microsoft-com:office:excel xml outout or just writing html and letting excel interpret it, but you should be fine with putting a standard html table with your header information in it before your data and another table after your data with your footer info.