<code>Public Function TimeDiff(ByVal Datum1 As String, ByVal Datum2 As String) _
  As Long
  Dim dDatum1 As Date
  Dim dDatum2 As Date
 
  <font color=green>' Datum1 umwandeln</font>
  dDatum1 = CDate(Datum1)
 
  <font color=green>' Datum2 umwandeln</font>
  dDatum2 = CDate(Datum2)
 
  TimeDiff = Abs(DateDiff("n", dDatum1, dDatum2))
End Function</code>

<code>If TimeDiff("10..10.2001 13:00:00", "10.10.2001 12:00:00") >= 30 Then
  MsgBox "Es ist mind. eine halbe Stunde vergangen!"
End If</code>