Hi,
I think I misunderstood your original post. It seems you are using conditional value based appearance functionality of the grid. In which case FilterRow event is not suitable. However I think you should be able to hook into InitializeRow and in the handler manually check if a cell matches the associated conditions and if so set/unset row's RowSelectorAppearance.Image. Column has ValueBasedAppearance which you can typecast to ConditionValueAppearance. This is the object that holds all the conditions that you setup design-time.
Hope this helps,
Sandip
If I understand you correctly, hook into FilterRow event of the grid. This gets raised whenever filter conditions are evaluated on a row. Here you can check IsFilteredOut property to either set or unset the row's RowSelectorAppearance.Image to exclamation icon.
Also of use might be row's MeetsCriteria method to check if the row passes or fails a specific column filter or filter condition. This can be useful if you want to check if the row passes filter conditions of a specific column.