Hi,
For once, a short question :-)
Is there a way to implement a custom group by logic, instead of the options available in the GroupByMode enumeration?
UltraGridColumn exposes a property, GroupByEvaluator, which you can set to an IGroupByEvaluator interface implementation (the interface has only two methods).
Note that the ICustomGroupByEvaluator will only get called to evaluate rows that are adjacent. So you may also need to implement a SortComparer on the column to make sure the column is sorted in the correct order before it is grouped.