Lookup across apps

Hey guys, 

With such a powerful tool I'm sure this is possible but I'm confused on how. I want to auto-populate details of an order when a single field is updated (the name of the product ordered). Effectively, that means I need to lookup the individual components required to make that product, and then populate the request in the app. So far, even using the workflow feature doesn't seem to let me reference the components of the product as saved in the other app. Can anyone help???