Welcome to Airtable !
If you could share a screenshot of your tables we can help you better.
Basically, what you want to do is Link the trucks between both tables, then you can create a new single select field (lets call it Current Locations). Once you choose Current Location in this single select, make sure you remove it from the previous entry though. You can then Lookup the value using the condition that the single select is Last Location.
Of course if you are worried you would forget to remove it from the previous entry, you can always make a small script that replaces the value for you. Better yet, a script can get the value of the last location to the other table directly.