<telerik:RadGridView x:Name="DynTableGridView" 
                             ItemsSource="{Binding DynTableses, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
  <telerik:RadGridView.RowDetailsTemplate>
                        <DataTemplate>
                          <telerik:RadBusyIndicator  IsBusy="{Binding ????? надо обратиться к DoWorkInput}">
                        </DataTemplate>
  </telerik:RadGridView.RowDetailsTemplate>
</telerik:RadGridView>

public class DynTablesViewModel:ViewModelBase
    {
        private ICollectionView _dynTableses;
        private bool _doWorkInput;
        
        #region Property

        public bool DoWorkInput
        {
            get { return _doWorkInput; }
            set { _doWorkInput = value; OnPropertyChanged("DoWorkInput"); }
        }
        
        public ICollectionView DynTableses
        {
            get { return _dynTableses; }
            set { _dynTableses = value; OnPropertyChanged("DynTableses"); }
        }

        #endregion
    }
}