I have used Imports Microsoft.Office.Interop and Reference of Microsoft excel is added to project/solution
Following are declaration
 Public xlsfilepath As String
 Public oxlsapp As New Excel.Application
 Public oxlsworkbook As Excel.Workbook
 Public oxlsworksheet As Excel.Worksheet
 Public oxlcellsrange As Excel.Range
 Dim xchar As String
Cell reading process from existing file
oxlcellsrange = oxlsworksheet.Cells(iRow, iCol)
MessageBox.Show(oxlsworksheet.Range(oxlcellsrange).Value)<----Here gives fatal error 
System.Runtime.InteropServices.COMException: 'Exception from HRESULT: 0x800A03EC'
Don't understand why?
Image is attached for that describes more.

 
     
    