Chen,

>You understood everything correctly. And I did set the ComboBox as you described. I should mention that the Employees bussiness object is registered as child of Departments bussiness object.
>
>I even tried to creat another bussiness object called DepartmentLookUp to be used as the data source for the department combobox. Even this failed!

Can you post all the binding property settings for the DataGrids and the Combo Box?

Regards,