ICE tickets at the fare Europa Spezial are valid from/to any Belgian station (ABS). This "Any Belgian Station" ticket allows you to use any train between your ICE station (Bruxelles-Midi/Brussel-Zuid or Liège-Guillemins) and any other station in Belgium, without having to pay any supplement.
Are both portions of the journey (the ICE part and Belgian IC) time specific or is this just the ICE part? I'm planning to do a journey from Frankfurt-Brussels-Kortrijk with a lunch-break in Brussels.