Creating a dynamic form in Excel Vba

I need to create a form in Excel; the size and elements of which depend on an array that I have populated in a macro.

So, basically, what I have is an array called Activities(x) with x elements.

x can potentially change each time the macro runs. I need to present this list with a checkbox next to each one that will result in a new array called ActivitiesNew(y) where y is (obviously) smaller than x.

I have no idea how to play with the userForm size (so that I can incorporate all the elements that should be shown) or with the caption of each checkbox so that the correct text is displayed.