[GameWizard]

Well I can't help you with the randomization code, that's something you can look for elsewhere, since the code is out there, you just need to find it.

As for your request, here is something that should get you on your way:

<if condition="is_member_of($bbuserinfo, 2)">
This will only show to Usergroup ID 2
</else>
$randombanner
</if>

<if condition="is_member_of($bbuserinfo, 3)">
This will only show to Usergroup ID 3
</else>
$randombanner
</if>

$randombanner refers to the code where the banner is randomized to your liking.