How to autopopulate field from relationship

I’m having trouble with auto populating a field when a record from a related module has been selected. I’ve found multiple threads about the subject but can’t seem to make any of them work. If anyone could help I would be most thankful.

In more detail:
I’ve got two custom modules I created - one is called Bookings and the other is called Items.
Items module contains services we offer. Name = Name of the service, price_c = Price of the service
Bookings module contains records for each booking made with the company

There is an Items One-to-Many Bookings relationship

When someone selects an item from the Items related field we would like a field called bookingprice_c to be autopopulated with details from price_c in the Items record selected.

What is the best method to accomplish this?

You can do it with a Workflow, or in PHP code using a Logic Hook.

Check the Documentation for these features, try it, and then please tell me specifically where you got stuck an dI can try to help you further.

Did you get this working? If so I would like to know how. Thank you