WCF ria service and Service Broker - how to work together?

Dear Gurus! 
Silverlight client uses a wcf service  to report about the changes in the mssql database.  If I understand correctly, there should be something like:

[OperationContractAttribute(AsyncPattern=true)]publicIAsyncResultBeginServiceAsyncMethod(string msg,AsyncCallback callback,object asyncState){returnAddEventChanges(callback);}public emergEvent EndServiceAsyncMethod(IAsyncResult r){
//  Response sent to the clientCompletedAsyncResult<emergEvent> result = r asCompletedAsyncResult<emergEvent>;
            result.Data.TimeDetected=DateTime.Now;return result.Data;}

        publicIAsyncResult AddEventChanges(){using(SqlConnection connection =newSqlConnection(connectionString)){using(SqlCommand cmd =newSqlCommand("Select id_event,name,description from dbo.events", connection)){
                    cmd.Notification=null;SqlDependency dependency =newSqlDependency(cmd);
                    dependency.OnChange+=newOnChangeEventHandler(WaitChange);
                    connection.Open();using(SqlDataReader reader = cmd.ExecuteReader()){}
// return IAsyncResult after WaitChange executed
                }}}publicvoidWaitChange(object sender,SqlNotificationEventArgs e){
// Forms answer with emergencyEvent type 	
        // and starts the next cycle of waiting for a response
        	  AddEventChanges();
       }

I am interesting how execute AddEventChanges() With a delay before executing  WaitChange procedure? Or how to make correctly?