IMP & Preferences - Can they be changed on the "fly"

[John]

When I had Imp 2.x running (nicely, BTW), I added a table to the MySQL 
database for Horde that stored an integer relating to what privledges a 
user might have when using the system.  i.e. Can he send mail? Y/N.  If 
sending mail OK, can he change the From address, Y/N.  This worked just 
wonderful for controlling various users.

I am trying to figure out if it is possible to change the prefs.php info 
either at login time, or later once they are read in to the cache.  I have 
tried several different routines with no success.  I am not strong on 
Object programing, but didn't have any difficulty in Imp 2.x.  Imp 3.x is a 
far cry from 2 and more compartmentalized which is not bad, just slightly 
out of my reach without some assistance.

I have the site setup to log in via IMP.  With this in mind, is it possible 
to control these pref's after user login?

I'd be grateful for any pointers or assistance along these lines...