If I select an extensibility addin of Excel, I'm able to debug my Add-In in Debug Mode with Excel, like
_application.ActiveWorkbook.ActiveSheet.Count
in Immediate window, but now I've moved to VSTO Excel 2003 Add-in, here I've goto following message while debugging,
Cannot obtain fields or call methods on the instance of type 'Microsoft.Office.Interop.Excel._Worksheet' because it is a proxy to a remote object.
I've enabled un-managed debugging in my application settings