Error 4207: Function requires a valid ADT argument

warum bitte bringt mir Set NewDoc = Doc.CopyToDatabase(ZielDB) den fehler “Error 4207: Function requires a valid ADT argument???

Function CopyAllDocs(qserver As String, qdb As String, zpath As String, qview As String) As Integer
   On Error Goto ErrHand
   '-1 = error
   '>0 = ok
   Dim QuellDB As NotesDatabase
   Dim QuellView As NotesView
   Dim ZielDB As NotesDatabase
   Dim Session As New NotesSession
   Dim vc As NotesViewEntryCollection
   Dim entry As NotesViewEntry   
   Dim Doc As NotesDocument
   Dim NewDoc As NotesDocument   
   Dim f As Long
   Dim ActDB As Integer
   
   
   CopyAllDocs = -1
   Set QuellDB = Session.GetDatabase(qserver, qdb, False )   
   QuellDB.FolderReferencesEnabled = True
   Set QuellView = QuellDB.GetView(qView)
   Set vc = quellview.AllEntries
   Set entry = vc.GetFirstEntry()
   Set Doc = entry.Document
   
   ActDB = 0
   Set ZielDB = Session.GetDatabase(qserver,Cstr(ActDB)+"_"+qdb, False)
   
   For f = 1 To vc.Count
      If f = DBSchnittmarken(ActDB) Then
         Call WriteLog("Wechsle zu Ziel-DB Nr: " & Cstr(ActDB), Info)
         Print "Wechsle zu Ziel-DB Nr: " & Cstr(ActDB)
         ActDB = ActDB + 1
         Set ZielDB = Session.GetDatabase(qserver,Cstr(ActDB)+"_"+qdb, False)
      End If      
      
      Set entry = vc.GetNthEntry(f)
      Set Doc = entry.Document
      Set NewDoc = Doc.CopyToDatabase(ZielDB)
      
      Forall ActFolder In doc.FolderReferences
         Call NewDoc.PutInFolder(ActFolder,True)         
      End Forall      
   Next   
   
   CopyAllDocs=1
   
   Exit Function
   
ErrHand:   
   Call ErrHandSub()
   Resume Next
End Function