I figured out a method to get this to work. By defining the position as fixed for the menu and setting the left position to the right edge of the document and the width to 0px (left:1024px; width:0px) it stays at a constant position. then the JS adjusts both the left position and the width at the same time, creating the illusion of it growing from right to left, when in reality it is moving 350px tot he left, and growing in width 350px to the right.