A bit lost in timers for TM module

Idea is following

I want to have dial timeout for 30 seconds, but only if I received 100 Trying in reply to INVITE. 

If no 100 Trying is received - I want timeout to be like 2 seconds.

100 Trying is indicator for me, that other side is alive.

As I got, fr_timer and fr_inv_timer is not what I’m looking for.