"Argument ist nicht optinoal" ???
Private Sub Workbook_Open()
Call OpenBook ' diese Zeile wird gelb markiert
End Sub
Function OpenBook(sBook As String) As Boolean
On Error Resume Next
sStr = Workbooks(sBook).Name
On Error GoTo ErrorHandler
Workbooks.Open sBook
OpenBook = True
Exit Function
ErrorHandler:
OpenBook = False
End Function