[Asterisk-Users] failed to go to next dial command

[MvB]

Hi,

I Looked through tons of pages sofar no luck. Hopefully some one could
tell me the directions or relevant commands for the following.

If I have an outbound call with a normal PSTN number from * to an other
* or IAX provider but that */provider is not reachable because of a
network congestion for example.

Then in that case I would like to go to a next dial command with a small
time out that would use my BRI to push the call out via a regular PSTN
provider:

I guess this is what I mean:

If 
   exten => _NXXXXXX,2,Dial(${IAX2_provider}/${EXTEN}) 
times out or returns error then dial 
   exten => _NXXXXXX,3,Dial(${CAPI_channel}/${EXTEN})  # goto telco 
else 
   exten => _NXXXXXX,4,Congestion/busy/invalid

Is this possible in Asterisk and what should be the approach?

Max.