[Freeswitch-users] DTMF disable a few secs after call starts

FS is in the media path of an IVR call. At the moment, the call is ulaw with DTMF in the audio I think coming into FS and leaving FS. The call is coming from an Asterisk server and going to an Asterisk server. Is there a way to disable FS from passing DTMF at some point in the call? For example, after 15 seconds, is there a way to get FS to stop passing DTMF events? Would I have to try to force asterisk to use rfc2833 when sending the call to FS and when accepting it back from FS?