asterisk users - Jul 2003 - * with external sip proxy

Hi all,
i'm tring ro use sip with an external sip proxy as vocal or ser.
 
My scenario is
 
Vocal or SER   ---->  Asterisk with cnah_oh323 ----->  Gatekeeper
 
I would like that sip termial register themself to Vocal or ser and the h.323
terminal to gatekeeper.
 
When i place a call from h323 side to sip side all work....
When a try to place a call form sip to h323 nothing happen
 
Does someone try this??? 
 
Any suggestion will be appreciate
 
 
Tnx
 
Marco