# scroll math not working just right

hi - i have a bunch of boxes inside a main box(mainFrame). The bunch of boxes are stacked vertically. I am trying to make the boxes scroll up/down with a scrollbar. you can see the demo here.

What i want to know is have i approached this all wrong? My concept was to get the height of the mainFrame mc, get the height of the scrollbar, get the ratio (mainFrame._height/scrllbar._height) of these two...then with setInterval, i would track the placement of the dragger(to the scrollbar height) and multiply that back to the ratio to reflect the size of mainFrame:

any ideas?
• ###### 1. Re: scroll math not working just right
with all scrollbar draggers (whether they are vertical or horizontal or something else) and all objects that will be scrolled (whether they are vertical or horizontal or something else) , you can assume that there will be 2 extreme positions of the scrollbar dragger and 2 extreme positions of the object being controlled and you can assume a linear equation will be used to give the position of the object depending upon the position of the scrollbar dragger.

so, in your situation of a vertical dragger and vertical movieclip:

mc._y=a*dragger._y+b; // where you solve for a and b using the two equations that result from knowing the 2 extreme dragger positions and the two corresponding extreme movieclip positions.