If his phone is enterprise activated on the BES there is only 1 primary account for calendaring, email (u can add more but they not enterprise accts) notes..etc. if you go into his phone and then into messages, select options then email settings and you should be able to tell the handheld not to received email, same thing for calendaring you can tell it to sync wirelessly or not. for a secondary email account just go the personal email setup wizard and add the BIS BB account from there.
Also, to not sync email. After the enterprise activation of his handheld delete the email service book, that will make the phone not receive emails.
Exchange 2007 cluster Admin
BES 4.14 Admin