Store Function in GUI

Hi there, I'm working on a GUI in which I calculate and plot different mathematical functions. This works really fine! But now I've got a problem which I can't solve. I want to have something like a 'Store-Function' in my GUI thats stores temporary (for example I calculate function f1 which I want to save before calculating the next function f2). The main AIM is that I want to plot one oder both functions later on. I thought of a Listbox with Checkboxes (where I can select, which functions shall be plotted). But as I saw, MatLab didn't provide something like this (except undocumented solutions). Does anyone got an idea how I can implement such a store function?

Thanks for your Help!