Detect DTMF bridged calls

I have a config in which I am trying to detect dtmf tones, here are the basics:

Outbound call is made
User presses an extension to call
Another outbound call is made via Dial
Once the two calls are bridged I want to be able to detect DTMF tones from the first user

What is the best way to do this? I tried applicationmap and couldn’t get it to work once the calls are bridged.