Formatting has nothing to do with importing data from MS Excel sheet.
Read this: Import Excel File to DataSet
If you use:
can NOT use
More about it, you'll find at: http://www.connectionstrings.com/excel
] and http://www.connectionstrings.com/excel-2007
Read carefuly about
But, if you got trouble with separator for thousends and decimals, try to manually change it
] or use CultureInfo (System.Globalization)
] class to change it programmatically (to imitate other settings).