Business Event - Function Question

 I'd like to create a Business Event that runs a function to find any HR job titles that have changed in a gvien time frame (the last hour or last day...).  I'm struggling with the code for the function to do this.  What's the best method to do this type of check?  The :old and :new bind variables are just for triggers, right?  Or should I be able to use them?  Is there a better way?

Any help would be appreciated.