I have a DGV that contains three columns: StoreID, DateStamp and GUID. I want to highlight duplicate or triplicate data if the StoreID exists more than once on the same DateStamp.

I have done some searching and I have found some ways to highlight columns or rows based on a certain value, but my needs require me to know if a StoreID exists more than once on the same day.

Any thoughts on how to program this would be much appreciated.