Private Function InListe(Liste As ListBox, ByVal sText As String) As Integer
  Dim I As Integer
  Dim Index As Integer
 
  Index = -1
  With Liste
    For I = 0 To .ListCount - 1
      If .List(I) = sText Then
        Index = I:Exit For
      End If
    Next I
  End With
 
  InListe = Index
End Function

If InListe(List1, "D:\") Then
  MsgBox "Ja - vorhanden!"
End If