snmptrapd & v3 user add

Hi,
I am trying to add v3 user to snmptrapd at runtime. Is there any standard 
interface for this?

I tried
$ snmpusm -v3 -u initial -l authNoPriv -a MD5 -A setupauthpass localhost:162 
create newUser initial
The snmptrapd does not seems to respond (although it responds for the engine 
id discovery).

I tried manually adding following entry to snmptrapd.conf ... This require 
restrat, which I want to avoid.
* createUser newUser MD5 myauthpass DES myprivpass

If no standard interface available, can I some how (by changing the code !! 
) enable snmptrapd to respond to snmpusm commands to add/update user entries 
at runtime?

thanks
chinmaya