window in shower waterproofing

Hi All,
I am installing a replacement vinyl window in the window in my shower alcove before CB and tiling. The replacement window will sit inside the existing aluminum frame.
Which is a better way to finish it for tile? CB and tile UNDER the vinyl frame? Or ABUTTING the vinyl frame? (Either way, I plan to use tarpaper vapor barrier and tilt the CB and tile slightly)
thanks!

Check out www.johnbridge.com for some suggestions. Not sure if there is a good solution on a replacement window. A new construction one might have better luck. Much better luck would be to install glass block. You'd still get some light, but you can get privacy glass, and you will be able to make it waterproof.