Hi Krit,
Not sure this is a good idea.
But you can try this.
1. Create another custom BO same as existing BO
2. Create data source from new BO (before copying the existing data)
4. Copy existing data to new BO.
5. Create a combined data source using data source from new BO and data source from old BO.
That might work? That's all I can think of.
Best Regards,
Fred