Creating USM user at run-time, NOT through snmpUsmMIB, is it possible?

Hey,
 
The snmpUsmMIB allows creating new USM users only by cloning existing
ones.
I want to allow creating new users from scratch, during run-time.

 
1) Would this mean hacking into net-snmp data structure of the
usmUserTable?
2) Or Is there an API for that? (that includes building an authorization
key from the pass-phrase and engineID)
 
Thanks,
Erez.