I am thinking of a situation like this: you are engaged in combat, you take a full attack action, so your only action left is a 5' step, which you can take right after your attacks, but could you delay it like this: say when my opponent attacks me, I'll step back, ending out of his reach, and he wastes his attack. He can follow with his 5' and keep attacking, but you ruined his first attack. Could you do that?