Email alert to users using CCK fields as a filter

Hi all,

I am building a job site, I want a user to be able to receive an alert when a particular kind of job is entered into the site. I am using CCK to provide a select list of the types of jobs that are available.

there are 2 sides to this, how the user subscribes to the type of job, and the actual sending of the job on submission.

Thanks in advance
t