Desperately need mixed data sources for ComboBox Adv and Cell

Hi there,
I'm loading a GGC from and XML. That's all fine and good. One of my columns will have a CellStyle set to combo box and have 3 possible choices. The data in the XML will be one of the choices. So, when the grid populates the combo needs to have the value that comes from that record. An external ComboBox will have the same behavior and display the combo setting for that row. User will then edit the record using the combo choices, either with external combo or grid combo.
My question is: is there a specific way to do this synchronization or should I simply set the cell combo = external combo, and let the grid values handle themselves and load the combo as they come in?
Basically, I want the combos to reflect the incoming record value which should then be editable with the same combos.

Thanks vm.

Hi VM,

Here is a minimal sample that shows you "How to bind the ComboBox in a GroupingGird?"
GridANDcomboBoxBinding.zip

Best regards,
Haneef