Conditional Redirect Upon New Subscriber Registration

Hello. Can anyone suggest a way to setup a conditional redirect dependant on information a subscriber entered when registering on my WordPress-backended site?

I am using the Cimy User Extra Fields plugin to enter additional user information. I would like to add a field to give registering users the option to be added to my weekly announcement list to keep them regularly updated with the goings on at my website. I can make the extra field easily enough, and I can add users to the announcement list too. However, what I do not know how to do is change the registration process, so that prior to completion a command is sent to the announcement-list-bot to send them a confirmation of their subscription.

I would be very grateful, if someone could at least point me at the PHP file in WordPress that I need to hack to get this done.

Thanks. 🙂