Macro to find column with duplicates, for each of those check another column for duplicate

Hello,

I've been trying to hack together code that will let me do the following:

1) In a certain column find duplicates.
2) For those duplicates check another column for duplicates
3) If found, highlight the rows.

I have searched and found a thread which seemed an almost exact match but now I'm stuck: http://www.excelforum.com/excel-form...lete-rows.html

The attached file should be helpful
tester.xlsx

The code I have found in the thread mentioned got me far, but now I'm stuck. Also I must admit that I do not know what I am doing. That is because the code does not have enough comments too explain what it does.

Sub MG30Jun57()
Dim Rng     As Range
Dim Dn      As Range
Dim Twn     As String
Dim oMax    As Integer
Dim Rw      As Range
Dim nRng    As Range
Dim temp    As Range

Dim K
Set Rng = Range(Range("B1"), Range("B" & Rows.Count).End(xlUp))
    With CreateObject("scripting.dictionary")
        .CompareMode = vbTextCompare
    For Each Dn In Rng
        If Application.CountIf(Rng.Offset(, 2), Dn.Offset(, 2)) > 1 Then
        If Not .Exists(Dn.Value) Then
                .Add Dn.Value, Dn.Offset(, 4)
            Else
                Set .Item(Dn.Value) = Union(.Item(Dn.Value), Dn.Offset(, 5))
            End If
        End If
        Next Dn

For Each K In .keys
    oMax = 0
    
    For Each Rw In .Item(K)
        oMax = Application.Max(Len(Rw), oMax)
        If Len(Rw) = oMax Then Set temp = Rw
    Next Rw
 
    For Each Rw In .Item(K)
        If Not Rw.Address = temp.Address Then
            If .Item(K).Count > 1 Then
                If nRng Is Nothing Then
                    Set nRng = Rw
                Else
                    Set nRng = Union(nRng, Rw)
                End If
            Else
                If nRng Is Nothing Then
                    Set nRng = Rw
                Else
                    Set nRng = Union(nRng, Rw)
                End If
            End If
        End If
    Next Rw
 Next K

End With
nRng.Interior.ColorIndex = 7
MsgBox nRng.Address
'nRng.EntireRow.Delete
End Sub

The result of the above code is highlighting a couple (wrong) cells. I know I should get rid of the Union declarations, but I don't know how to make sure the correct rows are highlighted. Also I do not understand how this code exactly finds duplicates in the first column, saves the rows which are dupes, and then checks for duplicates in those rows but in another column.

As far as I understand it this will get all the entries in de B column, then put them in a dictionary array. But then it starts counting (I do not understand why) and after that I just do not have the skills to understand the code... yet .

Any help would be greatly appreciated!