waterproofing spray for satin shoes?

[PlateSpinningAtAllTimes]

I've bought some lovely expensive (by my standards) shoes for my wedding in July and they come with a little note saying that you need to spray them with waterproofing stuff. However they're made of satin I'm worried about wrecking them! The sprays I've found in shoe shops all seem to be for leather/suede etc.
Any ideas?
www.johnlewis.com/215289/Product.aspx
Thanks!

Doh!

bump?

Scotchguard says you can use on satins and silks.

If you protect them you can't have them dyed later, I think.

Ah, thank you very much! Yes, the label warns about not being able to re-dye but I like the colour I've chosen so not a prob :)