Limiting Trunk Call Duration

I have been using asterisk for a week so obviously not very experienced. I would like to limit the call duration on an outgoing trunk call so that on expiry of the timeout the call hangs up.

I have been looking at TIMEOUT(absolute) but have no idea where this would be placed.

Is it possible prior to the timeout to play a message to indicate that the call is going to clear?

Many thanks

check out the flags associated with the Dial function in extensions.conf. These are intended to support a calling card type application it seems like, probably has everything you need.