Excel VBA Duplicates in one columns unique in another - vba

Question

I have been attempting to solve this for a couple of days and have been able not come up with or find a similar solution. I am trying to highlight duplicates in a single column where their are distinct values in another.
For example occasionally in column G there are duplicate names but they only need to be marked(highlighted) when the value column D is unique. So using the example below the end result should only highlight Elizabeth Moore.
Column D Column G
116023339 Alan Fluder
116023339 Alan Fluder
116023347 Elizabeth Moore
116025757 Elizabeth Moore
116025048 A. Lavoie
If it helps below is the code I used as my starting point.
Sub test()
Dim cel As Variant
Dim myCell As Variant
Dim myrng As Range
Dim myRange As Range
Dim CellValue As Long
Set myrng = Range("G2:G" & Range("G" & Rows.Count).End(xlUp).Row)
Set myRange = Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row)
For Each cel In myrng
If Application.WorksheetFunction.CountIf(myrng, cel) > 1 Then
For Each myCell In myRange
If Application.WorksheetFunction.CountIf(myRange, myCell) = 1 Then
myCell.Offset(0, 3).Interior.ColorIndex = 6
End If
Next myCell
End If
Next cel
End Sub
I should add that my current solution now is to separate the loops where one highlights all the column G dups then the second loop unhighlights where column D is duped.

Answer 1

If you can use formulas #Tim's suggestion works well. To fix the VBA:
Option Explicit
Sub test()
Const ROW_OFFSET As Byte = 2
Dim cel As Range
Dim rng1 As Range
Dim rng2 As Range
Dim cRow As Long
Dim lRow As Long
Set rng1 = Range("G" & ROW_OFFSET & ":G" & Range("G" & Rows.Count).End(xlUp).Row)
Set rng2 = Range("D" & ROW_OFFSET & ":D" & Range("D" & Rows.Count).End(xlUp).Row)
With Application.WorksheetFunction
For Each cel In rng1
If .CountIf(rng1, cel) > 1 Then
If .CountIf(rng2, rng2.Cells(cel.Row - (ROW_OFFSET - 1), 1)) = 1 Then
cel.Interior.ColorIndex = 6
End If
End If
Next cel
End With
End Sub
The inner For is not needed if columns are synchronized
I used the ROW_OFFSET constant to emphasize the alignment between columns
.