Conditional Formating

Hi,

I have a spreadsheet relating to students behaviour for the whole school. I would like to show duplicate incidents as staff think they have doubled up and want to delete the duplicates.

I have tried Conditional Formating - Highlight duplicates, but this isn't very helpful, it either highlights the whole sheet, or nothing at all.

the columns are: student name, registration group, incident type, date, staff member involved.

does anyone have any ideas of what is the best way to show duplicates.

thanks