'Umwandlung eines String ("0000" bis "2359") in eine Date-Variable
'Bei unbrauchbarer Eingabe im timstr-Parameter wird Rückgabe false
Public Function TryParseDate(ByVal timestr As String, _
  ByRef timedt As Date) As Boolean
 
  Dim h_str As String, min_str As String
  Dim h As Integer, min As Integer
 
  If Len(timestr) < 4 Then Exit Function
  h_str = Left(timestr, 2)
  min_str = Right(timestr, 2)
  If Not IsNumeric(h_str) Then Exit Function
  If Not IsNumeric(min_str) Then Exit Function
 
  On Error GoTo fehler
  h = CInt(h_str): min = CInt(min_str)
 
  If h < 0 Or h > 23 Then Exit Function
  If min < 0 Or min > 59 Then Exit Function
 
  timedt = CDate(h_str & ":" & min_str)
  TryParseDate = True
 
fehler:
 
End Function