Replace with silence

I am trying to work with Logic 10. Currently i use Adobe audition for editing my vocals and podcast. While editing I often use the "replace with silence" keyboard command. This allows me to highlight and area with the marquee tool and replace the highlighted locater area with silence While editing. Not Delete the area creating another region or snapping it together so the track is shorter bringing the words together. I would like to REPLACE the marquee marked area with Silence in logic. Is it possible with Logic and, if so, what is the keyboard command.

Also I realize that automation allows the edit to lower the volume on the area but doing that 20 or 30 times in a track is a huge amount of extra time. I would like a fast keyboard command to accomplish this