Tell him to masturbate himself and stop before the orgasm, and tell him to do it 10x. So tie him very tight and put your foot close to his dick, the one way that he can cum is trying to rub his dick in your foot. If you can, tie him without any movement, it will be funny to see him suffering.
You can set a timer to him, do some pauses, leave him there tied. Came back and give him another chance.
Put a butt plug in his ass, ask him to beg you to help him.
At the end you decided if he will be have or not an orgasm today.