User interface - scrollbar & adding elements

Question

Hi,

I'm trying to create a user interface, where I should be able to add elements from within the application, and order them correctly.

I'll try to describe it as clear as possible, with a little help of the screenshot in below.

I want to be able to add buttons (via code) to the list, every time one button after another (is it possible to sort these buttons as well?).
When the list of buttons exceeds my window or grid size, I want to be able to use a scrollbar (as shown in the screenshot).



How should I be able to do this?

Any help is appreciated!

Thanks in advance!


Greetz!