asterisk users - Mar 2009 - Recognizing the "making progress" notification

Hello all,

I have an extension like this in my test box:

exten => _XXXXXXXX,1,Answer()
exten => _XXXXXXXX,n,Playtones(350/100,0/750)
exten => _XXXXXXXX,n,Dial(SIP/${EXTEN})

The idea is that occasionally the SIP peer might take a few seconds to
connect the call, and this provides an in progress sound instead of
silence.

I don't want to provide a "ring" tone followed by a busy tone etc.
I
feel that this confuses users.

What currently happens though is that Playtones continues until Dial
actually connects the call... if I implemented this, the user would
never hear the ring tone, which is disconcerting.

What I am not sure how to do is how to capture that the sip peer is up
to making progress and then switching to playing a dial tone, busy
tone, congested, etc.

I thought about using a goto after Dial and jump to ANSWERED, or BUSY,
etc... but this doesn't allow the end caller to hear the ring tone and
only handles it for BUSY or CONGESTED.

How do I go about doing this?

Thanks in advance

Mikel