// Get a service used to work with express report
var eaxMdService = expressBox.getService();
// Get express report document
var eaxAnalyzer = expressBox.getSource();
// Determine arguments for callback function
var args = new PP.Mb.Ui.PropertyChangedEventArgs({   
    PropertyName: PP.Exp.Ui.ControlType.DataSources,
    Metadata: "Report", // Open express report
    TypeUpdateData: [PP.Exp.Ui.ViewTypeUpdate.PropertyBar, PP.Exp.Ui.ViewTypeUpdate.DataView]
});
// Determine callback function
var onPanelChanged = function (n, t) {        
    var chartView = expressBox.getDataView().getChartView();    
    t ? (chartView.DataChanged.fire(chartView, t.Args), t.Args.fireCallback(n, t)) : chartView.DataChanged.fire(chartView, t);
};
// Display dialog for loading report from file
eaxMbService.setSourceFromFile(eaxAnalyzer, PP.Delegate(this.onPanelChanged, eaxMdService, args));