User Changes Email Address hack, help?

[NTR Plus]

I can't seem to find a hack that would force an already registered member that changes his email address to go through the activation procces to assure it valid.

I see people on my board (no duplicate email address allowed) just changing the existing email address to something bogus and then re-registering with a new name. Easy way to make multiple names.

Is there a hack that will force them back into the "awaiting email verification" que if they change there email addrerss?

[Xenon]

it's already in vb:
member.php:
if ($verifyemail and $email!=$bbuserinfo['email'] and ($bbuserinfo['usergroupid']==2 or $bbuserinfo['usergroupid']==3)) {
$newemailaddress=1;