Is it possible to create a filtered drop down menu. For inventory's sake.

For example:


I manage a car lot, and I want to assign a car to a specific lot number.

So i create a product called "New Car" and I want to assign it to a lot space.

My drop down has lot spaces such as a-1 a-2 a-3 a-4
Lets say I choose A-2.


Later on that day I get another car and I want to assign it to a lot space. I want to have the drop down not include A-2 because A-2 is being used by the other car.

so my dropdown options should be a-1 a-3 a-4



Make any sense?
Is this possible?