Since Descriptors.AddGroup() doesn't return the descriptors you have to get a little creative. You can do a Get for each radio button, and then set the DataSourceUpdateMode. Something like this:
PatientCBM.Descriptors.Get(rbAgriWorkNo).DataSourceUpdateMode = DataSourceUpdateMode.OnPropertyChanged;
PatientCBM.Descriptors.Get(rbAgriWorkYes).DataSourceUpdateMode = DataSourceUpdateMode.OnPropertyChanged;