If you need to do a start_dtmf on the B leg then just use uuid_broadcast:

uuid_broadcast <uuid> start_dtmf

Keep in mind that uuid_broadcast will let you execute an arbitrary app on any leg. Check out the wiki entry:
http://wiki.freeswitch.org/wiki/Mod_commands#uuid_broadcast

-MC

On Wed, May 30, 2012 at 10:23 AM, Michael Lutz <mytemike72@gmail.com> wrote:
Ok, but with if I do an originate with a &(park) and bridge the calls
later using the api bridge command using ESL.

When I want to listen to the DTMF's generated by the originated
(called) number, I shoul use {execute_on_answer=start_dtmf, ..}
or do I need to specify the 'b-leg' and if so, how?

Regards,
Mike.