Derived property rendered in a 1:1 association

[L Eder]

Hi members:

i have this:

Child class:
    String prop1;
    String prop2;

and

Parent class:
    private SortedSet<Child> collec = new TreeSet<Child>();
    public Parent add (final Child child) {...}

How can i have prop1 + prop2 rendered when add() is executed?
Currently is prop1 the one being, by default, rendered in the Add
dialog's child drop-down control.

Thanks in advance, Eder