2 cellulles seulement

Private Sub Worksheet_Change(ByVal Target As Range)
Select Case Target.Address
    Case "$A$5"
        Range("$A$2").Select
    Case "$A$2"
        Range("$A$5").Select
End Select
End Sub

Option Explicit
Private Sub Workbook_Open()
    Sheets("a").Activate    ' nom adapter
    Range("a2").Select
End Sub

Option Explicit
Private Sub Worksheet_Change(ByVal c As Range)
    If c.Address = "$A$2" Then Range("a5").Select
    If c.Address = "$A$5" Then Range("a2").Select
End Sub