Hi DW,
You can achieve this by dynamically updating the datasource of filterbar's comboboxes when the data gets updated in the grid's DataSource.
Please refer to this sample.
http://websamples.syncfusion.com/samples/Grid.Windows/F62562/main.htmIt updates the FilterBar's datasource when the data is being updated in the grid's datasource programmatically.
Best Regards,
Saravanan