Getting the old value ????

Socram,

If you are looking for code to do this, you could insert the following into that sheet's code module (right-click on sheet tab and choose 'View Code'). This will ask the user if they really want to change the value in A1 whenever that cell's value changes, and if not it will revert to the previous value.

Private Sub Worksheet_Change(ByVal Target As Range)
Dim ans As String
Application.EnableEvents = False
    If Target.Address = "$A$1" Then
        ans = MsgBox("Are you sure you want to do this?", vbYesNo, "Warning!")
        If ans = vbNo Then Application.Undo
    End If
Application.EnableEvents = True
End Sub