Bob,

There is no built-in way to do this, but you could achieve it by using a DrawFilter. 

Something like this:

 class HighlightingDrawFilter : IUIElementDrawFilter

    {

        public bool DrawElement(Infragistics.Win.DrawPhase drawPhase, ref Infragistics.Win.UIElementDrawParams drawParams)

        {

            switch (drawPhase)

            {

                case DrawPhase.BeforeDrawBackColor:

                    drawParams.Graphics.FillRectangle(new SolidBrush(Color.Yellow), drawParams.Element.RectInsideBorders);

                    return true;

            }

            return false;

        }

        public Infragistics.Win.DrawPhase GetPhasesToFilter(ref Infragistics.Win.UIElementDrawParams drawParams)

        {

            if (drawParams.Element is ColumnHeaderUIElement)

            {

                DateTimeRange header = (DateTimeRange)drawParams.Element.GetContext(typeof(DateTimeRange));

                if (header.StartDateTime < DateTime.Now && header.EndDateTime > DateTime.Now)

                {

                    return DrawPhase.BeforeDrawBackColor;

                }

            }

            return DrawPhase.None;

        }

    }

Let me know if that works for you.