div based dhtml zoom box will not draw!!!

dhtml gurus!
i want to click and drag a div based dhtml zoom box on an image. i can
get it to draw when the drag is from left-top to right-bottom but not
when it's from right-bottom to left-top.

// this is for the drag from left-top to right-bottom. works like a
breeze
element.style.width = event.x - element.style.pixelLeft
....similar for height

// this is for the drag from right-bottom to left-top. doesn't work
element.style.width = element.style.pixelRight -event.x
....similar for height

help me here!
jzs