wpf listbox select its value when we click on vertical scrol

hi
i have a list box in which i have binded a list(numeric value 1 to 700) , i want that if i am changing the value through up and down arrow[verical scrollwing) of list box it should select the present value or the display value rather than on my click event.
its in wpf.
write now i am using selection changed event of list box.

listbox is a wpf control .

want to execute code on moving the scroll bar up and down with mouse