Dim ex As New Excel.Application
 
Private Sub Form_Load()
   Dim exwb As Workbook
   Dim answer As Long
   ' Excel-Workbook temporär einrichten
   Set exwb = ex.Workbooks.Add
   exwb.Sheets("Tabelle1").Select
 
   ' Werte einfügen und Ergebnis holen:
   ActiveSheet.Cells(1, 1).Value = 12
   ActiveSheet.Cells(1, 2).Value = 13
   answer = Application.WorksheetFunction.Sum(Range("A1:B1"))
   MsgBox answer
 
   'Temporäre Worksheet beenden
   exwb.Saved = True
   exwb.Close
   ex.Quit
   Set ex = Nothing
End Sub