Trigger Help!! -- need to create a record (custom)

I have 2 custom objects application and recommender , in the application I have a field name as recommender email address .So, I need to come up with an trigger such that when an recommender email address is filled , the trigger should be fired which in turn creates a recommender object which is associated with an application and application ID should be populated.

I would really appreciate any help in solving this...any ideas, solutions are most welcome....