Cancel running only one module

[Josef Hajas]

Hello,
I'm implementing pam_bioapi (for using my fingerprint reader) and I
want to implement possibility to cancel running biometrics operation.
Let's say I have this config:
 auth     sufficient    pam_bioapi.so [+some parameters]
 auth     required     pam_unix.so

and I would like have some cancel button in application (for example
in gnome-screensaver) which cancel only authenticate of pam_bioapi but
still try to authenticate by pam_unix. Is there some standard way how
to achive this? I had an idea to use pam_conv and return error, but I
can't be sure that some pam_conv come after user press cancel. I need
something I can call from application since pam_authenticate()
running.

Thank you

Josef Hajas