AX 2009 alert to external web service

I want to send Information to an external web service when Status on SalesLine changes. I can write all the code to get the information, put it into the correct format and send it to the web service, but I don’t know how to make it run when a change occurs. I think I want the same functionality as change-based alerts, but doing something else instead of sending alerts. What is the best way to go about this?

I’m new to this, so pointers to where I can find more Information will be greatly appreciated.