[flexcoders] anchoring Image to right of Canvas with % value?

[Mic]

I am trying to duplicate the html css:

img#door {
        position: absolute;
        height: 98%;
        width: 38%; 
        top: 1%; 
        right: 18%;
}

but very few of the Flex layout attributes accept a percentage. How do
I anchor the image at 18% from the right side so that when the Canvas
shrinks the image stays in its relative position? image.right takes an
absolute pixel value in Flex. TIA,

Mic.