Feathering a selection outwards after making a selection?¿

If I have mad a selection with say an ellipse marque, of say 100px and now I want to fether that same selection outwards, ie to start the feather 10 px outward of the 100px selection so that the 100th px has a 100% transparency and the 110th px has a transparency of zero,thus making the new selection 110px, how could I go about doing it. With the current feathering of the selection, it feathers only in the marquee already selected, not outward, and you cannot place negative feathering px. I know that there is most likely some sort of a ration where you would expand the selection by a certain amount of px, and then apply a ratio of feathering to it to enalble it to feather outside of the 100px marquee. what is it if it exists, and is there another way of doing this that is easier?

Try making the elliptical marquee, feathering, and then doing ctrl+shift+I to invert the selection. See if that is what you're talking about.

I'm not really sure of the mathematics of the feather tool, but why don't you just expand the selection by 10px and then feather it? Or make a new channel and then blur it?

tom

*edit - I just read your post again and this isnt really what you wanted. How about making a black rectangle ... then giving it a 10px black outer glow. Then flatten ... and use it for your selection? With the outer glow you could choose your opacity and a whole bunch of other options. I dunno.

Here's what I would do... I would either:
1)make a 110px circle and feather it 10px.

2)make the 110px circle--bring it into quick mask mode--give it a gaussian blur of 10px

Hope this helped.