JQuery :: Each Click Increases The Top Position By 100px?

I have this case:1) A #box that works as a container, it has overflow:hidden and position:relative.2) A #dynamic div that is inside of the #box, it has a padding:0 that gives it a height greater than its parent, it has position:absolute3) Inside the #dynamic div there are a random quantity of divs with the class of .item. There are two anchors, one anchor when clicked increases the top position of the #dynamic by 100px, the other anchor does the opposite.This is the code I tried:The problem with my code, is that when the anchor is clicked it only changes to 100px the value of the top position, instead of increasing its value by 100px each time it is clicked.By the way, the #dynamic div must always be in sight within #box, to prevent that many clicks send too far the position of the #dynamic. Making a big hole in the design.