You can use "cz excel converter" to Excel to xml Format, and this tool supports command line interface, so you can call it from your application, you can get demo version and more information from http://www.convertzone.com/excel_converter/help.htm
If you need batch convert converts PDF, XLS, HTML, XML, MTH, CSV, TEXT, DBF, Lotus 1-2-3, WKS, WQ1, SLK, DIF and more, "cz excel converter" will help you, it can convert many excel xls files at one time.
Please note: To support XML and MHTML format, you must install MS Excel 2002 or above.
regards
flyaga