code error, can any one tell me where is the error

Question

hi pleaze i wrote this code in vb, i want open excel sheet get some data from at run timel there is an error in line oBook.OpenLinks("c:/test2.xls",System.Reflection.Missing.Value,System.Reflection.Missing.Value) the error is "object reference not set to an instance of an object" then, please look to the line string1 = oSheet.Range("A1").Value string2 = oSheet.Range("B1").Value its true or not please tell me what can i do? how can i take data from an excel sheet CODE 'strings to put data from excel sheet Dim string1 As String Dim string2 As String 'open workbook in Excel Dim oExcel As Excel.Application Dim oBook As Excel.Workbook oExcel = New Excel.Application oExcel.Visible = True oExcel.UserControl = True Dim oBooks As Object = oExcel.Workbooks Dim ci As System.Globalization.CultureInfo = New System.Globalization.CultureInfo("en-US") oBooks.GetType().InvokeMember("Add", Reflection.BindingFlags.InvokeMethod, Nothing, oBooks, Nothing, ci) oBook.OpenLinks("c:/test2.xls", System.Reflection.Missing.Value, System.Reflection.Missing.Value) oBook.Activate() 'Get the first worksheet in the workbook so that you can 'make changes to it Dim oSheet As Excel.Worksheet oSheet = oBook.Worksheets(1) string1 = oSheet.Range("A1").Value string2 = oSheet.Range("B1").Value oBook.Save() oBook.Close() oExcel.Quit()