VBA- Match headers with multiple rows using a mapping table - vba

Question

I have a workbook with Sheet1, Sheet2, Mapping. I want to copy values from Sheet1 to Sheet2 based on both row/column headers in both sheets. The column headers are not the same, so I've created a mapping table in "Mapping" Sheet to match those headers.
The problem is that those headers are made from multiple rows- see this:
For example I need that (POS1 2019 Emp1) = (HR Department Employee 1).
The following code it's working but only if the mapping table looks like this:
(and also I've not added rows headers, I'm not sure how).
So please do you have any idea how can I make the mapping with multiple headers work? Should I put those headers in two separate named ranges? Any advice will be appreciated :)
Sheet1:
Sheet2:
Result that I want:
Public Sub test()
Application.ScreenUpdating = False
stack "Sheet2", "Sheet1", "Mapping"
Application.ScreenUpdating = True
End Sub
Public Sub stack(ByVal Sheet1 As String, ByVal Sheet2 As String, ByVal Mapping As String)
Dim rng As Range, trgtCell As Range, src As Worksheet, trgt As Worksheet, helper As Worksheet
Dim rngSrc As Range, rngDest As Range
Dim sht As Worksheet
Set src = Worksheets("Sheet1")
Set trgt = Worksheets("Sheet2")
Set helper = Worksheets("Mapping")
With src
For Each rng In Intersect(.Rows(3), .UsedRange).SpecialCells(xlCellTypeConstants)
Dim lkup As Variant
With helper
lkup = Application.VLookup(rng.Value, .Range("A2:B" & .Cells(.Rows.Count, "A").End(xlUp).Row), 2, False)
End With
If Not IsError(lkup) Then
Set trgtCell = trgt.Range("$B$2:$F$6").Find(lkup, LookIn:=xlValues, lookat:=xlWhole)
If Not trgtCell Is Nothing Then
.Range(rng.Offset(1), .Cells(.Rows.Count, rng.Column).End(xlUp)).Copy
With trgt
.Range(Split(trgtCell.Address, "$")(1) & 3).PasteSpecial
End With
End If
End If
Next rng
End With
End Sub