Well, an XLS is an Excel spreadsheet. An excel spreadsheet is not a "database" as programmers or web developers are used to using. For example, x10 supports PostGreSQL and MySQL. You access data from this software by creating tables in SQL, then querying them with SQL (structured query...
Are you already using a scripting language on your site? What kind of database do you have? If you use something like PHP and MySQL, I would recommend using PDO (PHP Data Objects) to access and query that database.
The manual entry: http://php.net/manual/en/book.pdo.php
Here's a reasonable...