public void setAvailability(Date dateAt, Object val) {

		// check, if date is already existing
		RosterAvailability r = checkAvailability (dateAt);
		if (r == null) {
			rosterAvailability.add(new RosterAvailability (dateAt.getTime(), (int)val));
			rosterChangeSupport.firePropertyChange("rosterAvailability", null, val);
		}
		else {
			Integer oldVal = r.getAvailabilityCode();
			r.setAvailabilityCode ((int)val);
			rosterChangeSupport.firePropertyChange("rosterAvailability", oldVal, val);
		}
		
	}