Resize button when using layout

[Macok]

I have listWidget on my form and I had problem with it, becouse when user was resizing window so it couldn't hold all listWidget's items - scrollbar wasn't appearing.
I solved it by marking "Lay out vertically" option, but now i can't resize button which is on the same form.

So is there way to change size of button when Vertical Layout is specified?
Or is it possible to force scrollbar to appear when form is too small?

Thanks in advance and sorry for bad english.