Tkinter multiple checkbuttons

I am using Tkinter for a simple application. I have an entry list with a variable size (a list of laptops). Then I ask the user to identify the cheapest and the most expensive ones. I use two loop-checkbuttons in front of these laptops, one column for the most expensive and one column for the cheapest such that a user is able to check one (and not the same) from each list . I dont know how should I make it. I use the choices for the next steps. Many thanks for your support in advance.