If he has a separate email account he can. On some sweeps you might need to clear cache between enters.
Bruce
There are some sweepstakes that eventhough the rules state one per person/email when my hubby tries to enter after me (even after clearing cookies etc) or me after him, we are told 'sorry you have already entered' ... those are the ones that read either street address or IP address as the basis for whether or not you have entered. But for the most part if the rules allow it you can both enter using the same computer.