Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, [A4]) Is Nothing Then
C = Application.Match(Application.EDate(Target, 1), Rows("2:2"), 0)
Range("AKC1:BAA1").EntireColumn.Hidden = False
Range(Cells(1, C), Cells(1, 1200)).EntireColumn.Hidden = True
End If
End Sub