I am trying to scroll an image with jquery from one point to another with jQuery

I am using the following code but cannot seem to get it to work

PHP Code:
var pos $window.scrollTop(); //position of the scrollbar
var windowHeight $window.height(); //get the height of the window

function test(startPosendPosscrollPoswindowHeight)
obj = $('#ios');
position obj.position();
console.log(position.top +  (startPos endPos)/ (scrollPos/100))
        return (
position.top +  (startPos endPos)/ (scrollPos/100))

$ios.css({'top':test(500120poswindowHeight) }); 
Nothing moves though. Can anyone give me a hint. TO be honest I am so turned around I don't know if I am anywhere close anymore