[SR-Users] User definable Ring Duration before forwarding

Hi I was wondering if the following scenario is possible and if it is how I would go about implementing it: I would like to be able read from a database a list of destinations associated with a given dialled number which are tried in order of priority with each destination having a user definable ring duration before the next destination is tried. i.e. A Call is received from the PSTN, the number the caller dialled is looked up, it has 3 destinations attached to it, the users deskphone which is configured to ring for 10 seconds before the call is forwarded to their Mobile phone with a ring duration of 15 seconds, which if unanswered would be redirected to the main switchboard IVR. I think im looking for the equivalent of the Asterisk Dial app, where you can specify a timeout as an argument, is this possible to do with kamailio? All examples I have seen use a global timer value, which is unsuitable for this requirement, as each user could define n failover routes each with a distinct timeout before the next route is tried. Currently I have got as far as querying the database to retrieve the data but im a bit stumped as to how to handle the timeout variable. Any ideas? Tim Chubb