Validation de donnée en interdisant * et cellule vide

Option Explicit

Private Sub Workbook_Open()
    Init
End Sub

Option Explicit

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    Dim Valeur As String
    
    If ValeurValide(LastColumn, LastRow) Then
        If (Not Intersect(Target, Range("B2:B8")) Is Nothing) Or _
            (Not Intersect(Target, Range("C2:C6")) Is Nothing) Then
            ' Store new position
            LastColumn = Target.Column
            LastRow = Target.Row
            LastColor = Target.Interior.ColorIndex
        End If
    End If
End Sub

Option Explicit

Const CarAutorises = "A,B,C,D,E"
Public LastColumn As Long
Public LastRow As Long
Public LastColor As Long

Public Function Init()
    Dim Ligne As Long
    Dim Valeurs As Variant
    Dim Valeur As Variant
    
    Sheets("Valeurs").Select
    Columns("G:G").Select
    Selection.ClearContents
    Range("G1").Value = "Usure"
    
    Valeurs = Split(CarAutorises, ",")
    Ligne = 2
    For Each Valeur In Valeurs
        Range("G" & Ligne).Value = Valeur
        Ligne = Ligne + 1
    Next
    Range("G1").Select
    Sheets("Demo").Select
    
    LastColumn = 0
    LastRow = 0
End Function

Public Function ValeurValide(NewColumn, NewRow As Long)
    Dim Valeur As String
    Dim Result As Boolean
    Dim Reponse As String
    
    Result = True
    ' Verify old position
    If ((LastColumn > 0) And (LastRow > 0)) Then
        Valeur = UCase(Left(Trim(Cells(LastRow, LastColumn).Value), 1))
        If ((Valeur = "") Or _
            (Valeur = ",") Or _
            (InStr(1, CarAutorises, Valeur) = 0)) Then
            Application.EnableEvents = False
            Cells(LastRow, LastColumn).Select
            Cells(LastRow, LastColumn).Interior.ColorIndex = 38
            Application.EnableEvents = True
            Reponse = MsgBox("Seuls " & CarAutorises & " sont autorisés", _
                vbOKOnly, "Erreur de saisie", "", 0)
            Result = False
        Else
            Cells(LastRow, LastColumn) = Valeur
            Cells(LastRow, LastColumn).Interior.ColorIndex = LastColor
        End If
    End If
    ValeurValide = Result
End Function