How to read Word, Excel Metadata by Vb.net ?

i want to read the metadata (such as author, keywords, etc.) of the Word, Excel file by asp.net (vb). How can I do that ?
is there any sample, reference site ?
thanks.
i found the following code online, but it return error for the 2nd statement (" Dim excelbook As New Microsoft.Office.Interop.Excel.Workbook ")
Public Sub ReadExcel(ExcelFileName As String) Dim Wapp As New Microsoft.Office.Interop.Excel.Application Dim excelbook As New Microsoft.Office.Interop.Excel.Workbook If Wapp Is Nothing Then Wapp = New Microsoft.Office.Interop.Excel.Application End If If excelbook Is Nothing Then excelbook = New Microsoft.Office.Interop.Excel.Workbook Else excelbook.Close() End If excelbook = Wapp.Workbooks.Open(ExcelFileName) Dim _BuiltInProperties As Object = excelbook.BuiltinDocumentProperties If Not _BuiltInProperties Is Nothing Th ...