Another easy button question from online play. According to the rules book, A player may discard a card’s shield token to prevent one damage or one focus token that would be placed on the shielded card by an attack or an enemy effect (i.e. it cannot prevent damage and focus tokens placed by its controller’s costs or effects). So can you place a shield on a card after a focus counter has been played on it by let's say Emperor Palpatine to take care of one of the focus tokens, or does the shield already have to be on the unit before the focus token goes on it?