Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo Fin: If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("B:B")) Is Nothing Then
Dim L%
Application.ScreenUpdating = False
Application.EnableEvents = False
For L = 2 To Range("A65500").End(xlUp).Row
If Cells(L, "A") = Cells(Target.Row, "A") Then Cells(L, "B") = Target
Next L
End If
Fin:
Application.EnableEvents = True
End Sub