Data validation rules will only pop up a warning if you enter an incorrect value in the validated cell. If they're picking a valid value from a validation list, it will never be incorrect and thus won't pop up a warning or prevent them from selecting a value. The only way to do this would be VBA, to my knowledge.
In VBA, you would just use the Worksheet_Change event and check to see if your range of validated cells has changed, for example:
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Cells.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("J3:J12")) Is Nothing Then
Application.EnableEvents = False
MsgBox "You have changed cell " & Target.Address & " to """ & Target.Value & """. If you did not intend this, please revise before continuing."
Application.EnableEvents = True
End If
End Sub
Bookmarks