Private Exl As New Excel.Application
 
Private WithEvents myTab As Worksheet
 
Private Sub Form_Load()
    Exl.Workbooks.Open "Name_der_Worksheet"
    Set myTab = Exl.ActiveWorkbook.Sheets("Tabelle1")
 
End Sub
 
Private Sub myTab_SelectionChange(ByVal Target As Excel.Range)
     ' .... hier dann Berechnungen
End Sub