I am copying you our answer from the support ticket you have posted with the same question, so the community can benefit from it.
As to the question at hand I would like to point your attention to two events in RadGridView - ValueChanged and CellValueChanged. The first one will occur when the user changes a value in an editor in RadGridView i.e. when he opens the combo box and selects different item - for example by default item 0 is selected, the user opens the combo editor and selects item 2. In this event, the cell value (radGridView1.CurrentCell.Value) will still be item 0however, the editor value will be item 2 (radGridView1.ActiveEditor.Value). To summarize this events notifies you about changes in the editor. As to the second event - CellValueChanged, it will be triggered when the user changes a cell value and commits it i.e. the cell goes out of edit mode.
More information about the events during the editing process in RadGridView can be found here: Editing events.
I hope that you find this information useful and you will be able to apply it in your scenario.
Regards,
Ivan Petrov
Telerik
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