Integration: non-webflow/spring app and swf 2

Spring Web flow Gurus,

Any pointers on my q are highly appreciated

With SWF 2.x, I need to integrate a third party authentication system( call it A) for which 'only have access to client libraries (jars) with appropriate APIs.

The application (call it B) is in Spring, SWF 2.x with
appropriate web-flow.xml in which all the action-states, action, etc. are all accessible to me to modify.


APIs of the client lib (of 'A') trigger a session redirect to the right auth server and post back the result to pre-specified servlet (in my control).



How can I model the following in SWF 2.x?

Web-flw of B (actions/states)
.
.
.

from one action will trigger the API to
redirect the session to A.
<q1: what should be state of the web-flow at this
point? while waiting for response> (<end-state ?>)
.
.

Once the response is posted back from A
Continue with rest of flow of B
.
.
.


Any sample code is highly appreciated.

PS: 'dont have access to A except the client libs to trigger
session redirect (not in my control)

Many thanks in advance