Question

I have found a macro that highlights duplicates

Public Sub MarkDuplicates()
    Dim iWarnColor As Integer
    Dim rng As Range
    Dim rngCell As Variant


    Set rng = Range("A1:A65000")
    iWarnColor = xlThemeColorAccent2

    For Each rngCell In rng.Cells
        vVal = rngCell.Text
        If (WorksheetFunction.CountIf(rng, vVal) = 1) Then
            rngCell.Interior.Pattern = xlNone
        Else
            rngCell.Interior.ColorIndex = iWarnColor
        End If
    Next
End Sub

But I need it to highlight all the duplicates except for the first instance. Perhaps a better way is to highlight the first instance of a unique value instead?

Answer 1

Check the range above the current cell to see if the count is greater than 1, rather than checking the whole range.

This modification will run also only test rows with data, and not run though 65535 cells if it’s not actually filled with anything

Option Explicit

Public Sub MarkDuplicates()
Dim iWarnColor As Integer
Dim rng As Range
Dim rngCell As Variant
Dim LR As Long
Dim vVal

LR = Cells(Rows.Count, "A").End(xlUp).Row

Set rng = Range("A1:A" & LR)
iWarnColor = xlThemeColorAccent2

For Each rngCell In rng.Cells
    vVal = rngCell.Text
    If (WorksheetFunction.CountIf(Range("A2:A" & rngCell.Row), vVal) = 1) Then
        rngCell.Interior.Pattern = xlNone
    Else
        rngCell.Interior.ColorIndex = iWarnColor
    End If
Next
End Sub