XL 2016 VBA - Comment passer une structure Private en argument d'une fonction ?

Private Type MONTYPE
    L As Long
    S As String
End Type

Private Type MONTYPE
    L As Long
    S As String
End Type

Private Type MONTYPE
    L As Long
    S As String
End Type

Sub a()
    Dim MT As MONTYPE
  
    MT = b
    MsgBox MT.S
End Sub

Private Type MONTYPE
    L As Long
    S As String
End Type

Function b() As MONTYPE
    b.S = "Fonction b du Moodule 2"
End Function

Option Explicit

#If VBA7 Then
    #If Win64 Then
        Private Declare PtrSafe Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
            Destination As Any, Source As Any, ByVal Length As LongPtr)
    #Else
        Private Declare PtrSafe Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
            Destination As Any, Source As Any, ByVal Length As Long)
    #End If
#Else
    Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
        Destination As Any, Source As Any, ByVal Length As Long)
#End If

Private Type MONTYPE
    L1 As Long
    L2 As Long
    S As String
End Type

#If Win64 Then
Sub b(MTAdd As LongLong, Lg As Long)
#Else
Sub b(MTAdd As LongPtr, Lg As Long)
#End If
    Dim MT As MONTYPE
    Dim FixedPart() As Byte
    Dim PtrString As LongPtr

    ' Copier uniquement les parties fixes (L1, L2, et le pointeur de la chaîne)
    ReDim FixedPart(0 To LenB(MT) - 1)
    CopyMemory ByVal VarPtr(FixedPart(0)), ByVal MTAdd, LenB(MT)

    ' Reconstruire les parties fixes
    CopyMemory MT.L1, FixedPart(0), 4
    CopyMemory MT.L2, FixedPart(4), 4
    CopyMemory PtrString, FixedPart(8), LenB(PtrString) ' Adresse du contenu de la chaîne

    ' Reconstruire la chaîne de manière sûre
    If PtrString <> 0 Then
        MT.S = PtrToString(PtrString)
    End If

    ' Afficher les valeurs
    MsgBox MT.L1 & vbCrLf & MT.L2 & vbCrLf & MT.S
End Sub

Private Function PtrToString(ByVal Ptr As LongPtr) As String
    Dim StrLen As Long
    Dim Buffer() As Byte

    ' Lire la longueur de la chaîne à partir de la mémoire
    CopyMemory StrLen, ByVal Ptr - 4, 4 ' Longueur Unicode

    ' Copier les données dans un tableau de bytes
    If StrLen > 0 Then
        ReDim Buffer(0 To (StrLen * 2) - 1) ' Chaque caractère = 2 octets (Unicode)
        CopyMemory Buffer(0), ByVal Ptr, StrLen * 2
        PtrToString = StrConv(Buffer, vbUnicode)
    Else
        PtrToString = vbNullString
    End If
End Function