For syf = 1 To Sheets.Count
Background of found records are painted and new borders are drew :
For Each mycell In Selection
If WorksheetFunction.CountIf(Selection, mycell.Value) > 1 Then
mycell.Interior.ColorIndex = 8
mycell.Borders.Weight = xlThin
mycell.Borders.ColorIndex = 44
If desired the processes can be recovered with "Undo Button".