Attach translated coordinate system to an object?

Hi,

is there a way to add a translated coordinate system / proxy to an object? Eg. in a normal case the top view of an object would be represented by X/Y, but I'd like to attach X/Y to a side-wall of a cube.

Currently for doing some CNC work I use to translate / rotate the object so I can generate some path on-top of the object. But if I could only attach a proxied coordinate system to it that would make the job for a 3+2 axis machine much easier.

thanks,
Markus