How do I make a field (column) appear from Custom Module 3 in Products where Layout is “car rental”.

CustomModule3 represents vehicle details (vehicle name, number of seats, type etc.).

I need to be able to show some of that information (number of seats, vehicle type) under Products with ‘Car Rent’ layout.

I’ve read around the forums and it seems I cannot simply “add” columns from CustomModule3 to Products (which is really strange since they are related).

It seems that the only solution is to create additional fields in Products (‘car rent’ layout) which get their value from fields in CustomModule3.

Can you tell me how to write a custom function to achieve this?