Dim col As Object
    Set col = CreateObject("System.Collections.ArrayList")

    For i = 7 To [d65536].End(3).Row
        If Not col.contains(CStr(Cells(i, "d").Value)) = True Then
          col.Add CStr(Cells(i, 4))
      
      End If
    Next
ComboBox3.Clear
If col.Count > 0 Then
    col.Sort
    ComboBox3.List = col.toarray
End If
Set col = Nothing

    For i = 7 To [d65536].End(3).Row
        If WorksheetFunction.CountIf(Range("d7:d" & i), Cells(i, "d")) = 1 Then
          ComboBox3.AddItem CStr(Cells(i, 4))
       End If
    Next

CreateObject("System.Collections.ArrayList")