I assume you mean a cron job? A cron job is triggered by time, not external events. If you wanted to use cron, you'd need to have it poll regularly (by time) to see if the queue is empty. It would be better to have code listening on the queue that does what you want - or calls the UNIX script - when a message is put on the queue.
I have proposed a solution of preparing MDB and then execute the cron job from it. But they came back saying there are few settings that can be done in WMQ 7 which could trigger a cron job.
Can any one help me .