Make Listbox To Be Used In Multiple Forms?

I am designing a degree audit program for school, and have a listbox where all the classes needed are contained. I have a separate form for each year (Freshman, sophomore, etc.), which also contain listboxes which are empty. The idea is to add the selected class from the first listbox into the empty listbox in the appropriate year form. However, to do this I would like to have the same listbox (the first one with all the classes) appear on each form, but still reflect changes made to it from other listboxes (classes transferred out of it).

To do this, would I need to create a listbox with global properties? Or would it be better to create a global function containing all the classes and have its contents called to the appropriate listbox?