asterisk users - Feb 2007 - Send DTMF's before the call is answered

Is there a way to send DTMF's to a channel before the call is answered?

For example, send DTMF's to a SIP channel after the 180 Ringing or 183 
Session Progress have been received from it, but before the 200 OK, or 
in the E1 side, after the Q931_ALERTING is received, but before the 
Q931_CONNECT. If I use Dial(SIP/XXXX,D(my_dtmfs)), it will wait until 
SIP/XXXX have answered to send the tones, but I need to do it before that.

Thanks a lot for your help.

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Attn.
Alvaro Palma