How to use IObservable in a different realm?

Question

I have observables x and y within SWT realm. I want to use their values to compute content for IObservableList z. The calculation can't be done in UI thread, so I have to write:

class Computer {
    private final IObservableSet x;
    private final IObservableList y;
    private final WritableList z = new WritableList();
    Computer(IObservableSet x, IObservableList y) {
       this.x = x;
       this.y = y;
       x.addSetChangeListener(new ISetChangeListener() {
           public void handleSetChange(SetChangeEvent event) {
              update();
           }
       };
       y.addSetChangeListener(new IListChangeListener() {
           public void handleListChange(ListChangeEvent event) {
              update();
           }
       };
    }

    void update() {
        Set xData = new HashSet(x);
        List yData = new HashList(y);
        // Calculation is to be done in a different thread and within special context
        Model.getTransactionManager().asyncExec(new Runnable() {
            void run() {
                List zData = numberCruncher(xData, yData);
                //can't assign to SWT reaml directly
                z.getRealm().asyncExec(new Runnable() {
                   void run() {
                      z.clear();
                      z.addAll(zData);
                   }
                });
            }
        });

    }
}

This smells so bad, I can't breath. The concept of databinding is completely buried with this calculate in a separate thread approach.

I've considered using ComputedSet for z with a custom Realm (using proper asyncExec), but there is no easy way to access x and y values from there. x and y could be bound to their proxies within custom realm, but that would duplicate memory usage and probably will pollute model thread with extra event processing.

Is there a smart way to get values of x and y from a custom realm to compute a value for a z observable?