How To Add Multiple Records Where Only One Number Changes

My boss wants to be able to add multiple records where only on of the fields will change. This is a repair record and in this scenario all the work done to the cars is the same. Same date, same place, same time etc. The only thing that changes is the car number

I would like to create a for that will allow him to enter all the information for place, date, cost, etc and then a field that will allow him to select a car from the dropdown and select add to list. He could then keep going and add as many cars to the list as he wants.