Conditional Formatting Of Duplicates Across Multiple Cells

I use the conditional formatting of duplicates within a column quite often. Now I am trying to highlight duplicates based on multiple cells in the same row. I can't seem to get a formula to make that work. I have four cells in separate columns but the same row, for example H2:K2, H3:K3, H4:K4, etc. I would like to highlight the four cells in that row if there is a duplicate of all four cells in another row. So if one, two or three cells are duplicates in the same column I do not want to highlight any of the cells, it should only highlight the group of four cells if all four cells are identical in another row. Pretty much the same way the default highlight duplicates works, just the value is spread across four cells.