I was able to get this working in our scenario using the approach of setting values on an editor for each cell in the InitializeRow event.

In our scenario we had a date where we'd want to let people pick the next date if the time was within 1 hour of midnight. Inside our InitializeRow event, I put code like this:

var rowObject = e.Row.ListObject as OurModelType;
if (rowObject == null) return;

var dateColumn = e.Row.Cells["EventDate"];
if (rowObject.EventTime.Hour >= 23)
{
    dateColumn.Activation = Activation.AllowEdit;
    dateColumn.EditorComponent = new UltraDateTimeEditor
    {
        MinDate = rowObject.EventDate,
        MaxDate = rowObject.EventDate.AddDays(1)
    };
}
else
{
    dateColumn.Activation = Activation.NoEdit;
}

I'm pretty sure this will not work.If I am wrong, then it would certainly only work once you set the UserEditorMaskProperties on the column to true. But I suspect the MinValue and MaxValue cannot be set on a single cell.

You could, of course, trap the BeforeCellUpdate event and validate the value against whatever you want.