Is it possible, with app.execDialog(), to get the selected parent node of a heir_box_list?

So when creating a dialogue using app.execDialog(), it is possible to have a hierarchical box list with the element type "hier_box_list".

It is then possible to get a return of the child node that is selected. However, I haven't find a way to get anything returned if I have a parent node selected.

I used the example 4 from the JavaScript API, page 84-87, to create the code below. Unfortunately this just returns a "undefined" when a parent node (like "Chapter 1", "Section 1", or "Section 2") is selected.

var dialog4 = {
    selection : {
        "Chapter 1" : {
            "Section 1" : {
                "SubSection 1" : -1,
                "SubSection 2" : -2,
            },
            "Section 2" : {
                "SubSection 1" : -3,
                "SubSection 2" : -4,
            }
        },
        "Chapter 3" : -5,
        "Chapter 4" : -6,
    },
    Return : "",
    initialize : function (dialog) {
        dialog.load({
            subl : this.selection
        })
    },
    subl : function (dialog) {
        var element = dialog.store()["subl"];
        this.Return = this.getHierChoice(element);
        console.println("\nSelection Box Hit: " + this.Return);
    },
    getHierChoice : function (e) {
        if (typeof e == "object") {
            for (var i in e) {
                if (typeof e == "object") {
                    var retn = this.getHierChoice(e);
                    if (retn) {
                        retn = i + ", " + retn;
                        return retn;
                    }
                    // if e > 0, we’ve found the selected item
                } else if (e > 0)
                    return i;
            }
        } else {
            if (e > 0)
                return e;
        }
    },
    commit : function (dialog) {
        this.selection = dialog.store()["subl"];
    },
    cncl : function (dialog) {
        dialog.end("cancel")
    },
    // Dialog box description
    description : {
        name : "My Novel",
        elements :
        [{
                type : "view",
                align_children : "align_left",
                elements :
                [{
                        type : "cluster",
                        name : "Book Headings",
                        elements :
                        [{
                                type : "static_text",
                                name : "Make a selection",
                            }, {
                                type : "hier_list_box",
                                item_id : "subl",
                                char_width : 20,
                                height : 200
                            }
                        ]
                    }, {
                        type : "ok_cancel",
                    }
                ]
            }
        ]
    }
};
function dotheDialog(dialog, doc) {
    dialog.doc = doc;
    var retn = app.execDialog(dialog)
};
dotheDialog(dialog4, this);

Does anybody know how I could have this return something if the user selects a parent node?