Showing only the latest record on a field

Hello! I am a very green user of this spreadsheet and want to develop a car rental admin app the problem I have encounter is that when I rent a car more than one time there are fields that start to show more than one value per example:

I have a worksheet where all cars are listed and another one where the contracts are made but is a car has been rented before the contract field shows every contract number that has been link to that car. I only need the latest one to show the old ones not but I do not want to unselect the car linked to the old records in the contract as it is needed for history purposes.

Is there a way to do this?