Silverlight 4 has the capability of accessing the COM object using the COM API. You can access any program installed in your PC using those APIs in Silverlight. You can open Notepad, Word, Excel or Outlook from Silverlight application. Here I will demonstrate you the step-by-step tutorial on opening an Microsoft Excel book followed by data sharing between the Silverlight application and the Excel Sheet. Here we will use a DataGrid which will load some customer information. Then we will pass the data to the Excel Sheet and then we will modify the data in the external application (i.e. inside the Excel sheet). You will see that, the modified data will reflect automatically to the Silverlight Application.