Comparison of 2 versions of Excel sheet

[NM123]

Hi All,
I have attached two xl sheet which are of different versions in the zip folder. I want to compare both the sheet and track the changes in a new sheet. Below is the my code, for some reason it is not working.
Can you please have a look into it.

 
Sub test()
    Dim a, i As Long, ii As Long, w(), temp, flg As Boolean
    With Workbooks.Open(ThisWorkbook.Path & "\OldVersion.xls")
        a = .Sheets(1).Range("a1").CurrentRegion.Value
        .Close False
    End With
    ReDim w(1 To UBound(a, 2))
    With CreateObject("Scripting.Dictionary")
        .CompareMode = 1
        For i = 2 To UBound(a, 1)
            For ii = 1 To UBound(a, 2)
                w(ii) = a(i, ii)
            Next
            .Item(a(i, 1)) = w
        Next
        a = ThisWorkbook.Sheets(1).Range("a1").CurrentRegion.Value
        For i = 2 To UBound(a, 1)
            If .exists(a(i, 1)) Then
                w = .Item(a(i, 1))
                For ii = 2 To UBound(a, 2)
                    If w(ii) <> a(i, ii) Then
                        temp = a(i, ii): a(i, ii) = ""
                        a(i, ii) = "Was : " & w(ii) & vbLf & _
                        "Now : " & temp
                        flg = True
                    End If
                Next
                If Not flg Then
                    a(i, 1) = ""
                    flg = False
                End If
            End If
        Next
    End With
    With ThisWorkbook.Sheets(2)
        With .Range("a1").Resize(UBound(a, 1), UBound(a, 2))
            .Value = a
            On Error Resume Next
            .Columns(1).SpecialCells(4).EntireRow.Delete
            On Error GoTo 0
        End With
    End With
     
End Sub

Hope this clears You.

Regards,
NM