Shrink Surface by 1mm

Hi,

Is there a way I can scale/shrink a closed surface so that its shrunk inwardly in all directions by 1mm? I created an object intended to be made with one material, but now we want to use two different materials. I’d like to shrink the inital design by 1mm, to be made with the first material, and overlay a 1mm material on top of this object. Is this possible?

I have tried to use the scale command and the boxedit command.

Thank you

One way _OffsetsSrf
http://docs.mcneel.com/rhino/5/help/en-us/commands/offsetsrf.htm