There is an odbc driver for excel. You can try to use this along with the odbc functions in php
http://www.php.net/manual/en/ref.uodbc.php, although I don't think the excel driver is supported. Obviously your web server would have to be a windows machine as well, because a linux one won't have the excel odbc driver! Your other options would be:
1) Save the excel file as a dbase file - php can read these
2) Save the excel file as a csv file - you could then parse this
3) Write/find and download a COM component that will allow you to give SQL queries for the excel file. Something like this would be pretty easy to write in VB6/
VB.Net