[Tsung] how to use parse_bidi

[Srivatsan Raghavan]

hey all, i'm writing a plugin for my company's custom protocol for  
tsung.  and the idea is you login first, then you test various  
commands in a single transaction.

atm i've put them all into various attributes in a single new tag.   
but it appears i can do roundtrip communications using parse_bidi, but  
i'm unclear how i can do
extended n-level communications like this, for instance
1) login -> login_id
2) if login successful ->   make_query_x( login_id)
3) if query_x_successful -> make_query_y(login_id)
4) logout(login_id)

is this possible ? if so, can anyone give me some help as to how to go  
about implementing it?