DataGridViewComboBoxColumn - Prevent some values from being selected

Hi,

I have a DataGridViewComboBoxColumn in a DataGridView control that is bound to a collection of objects and I need some values to be be flagged as inactive in that if a row contains a value that is now inactive but was selected in the past, it would still display. But when selected a new value from the popup list, the inactive values should not be available for selection.

If I remove the inactive items from my combobox source, the grid displays a blank cell value so this is no good.

Does anybody have any idea on this?