Das wäre eine Möglichkeit. Allerdings nicht getestet...
Code:
Dim Sek As Byte
Dim Ms As Integer
Dim Zaehler As Byte

Config Pinb.0 = Input
Config Portb.1 = Output
Config Portb.2 = Output

Alarmeing Alias Pinb.0
Ausgang Alias Portb.1
Led Alias Portb.2

Do
   Gosub Msek

   If Alarmeing = 1 Then
      If Zaehler = 0 Then
         Ms = 0
         Sek = 0
      End If

      Zaehler = Zaehler + 1

      If Zaehler = 3 Then
         Set Ausgang
         Sek = 0
      End If
      Do
         Gosub Msek
      Loop Until Alarmeing = 0
   End If

Loop
End


Msek:                                                       'Jede Millisekunde
    Waitms 1
    Ms = Ms + 1
    If Ms = 1000 Then
       Sek = Sek + 1
       Ms = 0
    End If
    If Sek > 10 Then
      Zaehler = 0
      Sek = 0
      Toggle Led
      Reset Ausgang
    End If

Return