Area cut out for glass

[flyingemt]

All, working a new shadowbox. Usually after I cut out the pattern, I use a 3/4" dado bit in my router to cut out the inset for the glass.

Thought of trying this with the CW but using the 3/8" to do the job.

Have the pattern laid out with the inset, using rectangle tool, but is there a way to set it for the 3/8" for the rectangle?

It just may be lack of coffee this morning, but thoughts?

Mike