sent to xml in with decimal type in columns

Hello

I am sending some data to xmlExcel as below:

when data is string:

returnString.Format("<Cell><Data ss:Type=\"String\">{0}</Data></Cell>", data);

when data is integer number:

returnString.Format("<Cell><Data ss:Type=\"Number\">{0}</Data></Cell>", data);

now how can I send my decimal column to excelXml?

thanks n advance