Bonjour,
copier cette macro sur la page code de la feuille concernée,
Private Sub Worksheet_Change(ByVal Target As Range)
Dim trouve As Range, isect As Range
Set isect = Application.Intersect(Target, Range("A:F"))
If Not isect Is Nothing Then
Set trouve = Range("G1:H8").Find(What:=Target, After:=Range("G1"), LookIn:=xlValues, LookAt _
:=xlWhole, SearchOrder:=xlByColumns, SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)
If trouve Is Nothing Then
Target = ""
MsgBox "nom interdit"
End If
End If
End Sub