VBA - Restriction of Copy/Paste on dropdown list not working when the file is shared

[Clemmye]

Hello,

Here's my first post and question.
So I've got an issue with a part of my VBA code when I share my file (the file needs to be shared unfortunately).
The trouble that I've got is that I use multiple DataValidation lists, and as I saw that some people were pasting their own data onto it (didn't find the origin yet), I tried to protect it (code below).
Also, in this code, there's a protectiong to restict edition on cells with formulas, and that part works fine when the file is in Shared mode.

However, the protection onto dropdown lists isn't working. I tested to see what was going off, and basically, the file considers that the data entered is valid when the file is shared (and also when I unshare it right before the vba does the event...)

I have no idea on how I could make this thing work :

Private Sub Worksheet_Change(ByVal Target As Range)
    
    'Does the validation range still have validation?
   If Not HasValidation(Range("ValidationRange1, ValidationRange2, ValidationRange3, ValidationRange4, ValidationRange5, ValidationRange6, ValidationRange7, ValidationRange8, ValidationRange9, ValidationRange10, ValidationRange11")) Or Not Intersect(Range("G5:G900,I5:I900,O5:O900,R5:R900"), Target) Is Nothing Then
        Application.EnableEvents = False
        Application.Undo
        Application.EnableEvents = True
        MsgBox "Impossible de coller des données dans cette cellule." & Chr(10) & _
        "Un menu déroulant est disponible." & Chr(10) & _
        "En cas de problème : xxxx.", vbCritical
    End If
    
End Sub

Function HasValidation(R) As Boolean
'  Returns True if every cell in Range r uses Data Validation
   On Error Resume Next
    HasValidation = True
    If R.Areas.Count > 1 Then
      For Each ar In R.Areas
          x = ar.Validation.Type
          If Err.Number <> 0 Then HasValidation = False
      Next
    Else
      x = R.Validation.Type
      If Err.Number = 0 Then HasValidation = True Else HasValidation = False
    End If
End Function

Thanks for all the help you could provide to me.

PS: I've tried to write the dropdowns lists on VBA... same trouble