In Custom Module, Get Field from Linked Module.

In Custom Module, Get Field from Linked Module.

Let's say I want to create a custom module called Calc. The Calc module contains a Lookup field to the Product module. On the Calc module I want to have a custom field that looks up the unit price of the associated product. In other words, based on the linked Product, I want to create a field in the Calc module that shows the product's unit price.