Thanks for the Great help every one...
I have redesigned the ring a bit shaper and used the trim and that worked great..!

And then I thought I would do the Inset command as SteveMacc mentioned, but I have not yet been able to make it work even with small numbers 0.2 and various separate height... like Burrman said.
So I decided to extrude ( Using the option both sides ) and that's working great so I could use the Boolean difference option

The extrude is working fine, but I don't understand why I get a hollow shell like this...

Thank You.
Tsiao