actually, you could set a modular value to hold the value of the scroll position. when clicking the up or down buttons the scrollbar position will change accordingly. in the .ValueChanged or .Scroll or both, just run a check on the current postion vs the stored value in your modular variable. if the current amount is lessthan the stored value, then they scrolled up. if it's more, then they scrolled down. now that you know the direction they went, dont forget to set the modular variable = to the current value so you can check it again when its clicked again.
i realize this post is quite old, but i figured it could possibly still help someone out.