Dim app As New Application
        Dim wb As Workbook
        Dim sheet As _Worksheet
 
        wb = app.Workbooks.Open("C:\test.xls")
 
        sheet = DirectCast(wb.Sheets(1), _Worksheet)
 
        'Zellen lesen
        For Each row As Range In sheet.Rows
            If String.IsNullOrEmpty(CStr(DirectCast(row.Cells(1), _
              Range).Value)) Then Exit For
            For Each cell As Range In row.Cells
                If String.IsNullOrEmpty(CStr(cell.Value)) Then Exit For
            Next
        Next
 
        'Zelle D1 schreiben
        sheet.Cells(1, 4).Value = "Roger Federer"
 
        wb.Save()
        wb.Close()