HELP! - How can I have a value in a list, for example

yes. this is possible.

This is not exactly what you are looking for, but with this simple app you can reference items from one list based upon a choice made in a corresponding list. food/cal lists

what you really want to do is learn to do a VLOOKUP. This is most easily done using a key.
Simple VLOOKUP
Moderate VLOOKUP (only because of the other items and there’s not a written tutorial)