Disabling purge menu in modcp

[swehack]

actually i was thinking of a solution that would not require rebuilding each upgrade, i found time out of my day to take a look at vBulletin and found something called BITFIELDS that are used to define permissions, i also find mysterious numbers in the moderator table of the database that could be definitions for permissions using these bitfields, i found the xml file includes/xml/bitfield_vbulletin.xml which defines the two bitfields i want to change, on lines 130 and 131

<bitfield name="canmassmove">256</bitfield>
<bitfield name="canmassprune">512</bitfield>

these are really the only permissions i want to remove from my moderators but i'm afraid i don't have time to go through vbulletin code and figure out how the bitfields are calculated so thats why i thought i'd ask here where there obviously are a few vbulletin hackers with the experience i need

edit: i have read the information on this link http://www.vbulletin.com/docs/html/main/bitfield_xml but it does not mention how the bitfields are calculated or how i can recalculate them in order to change the bitfield permissions in the database