[Micha]

... can be done:

- open the material properties
- highlight an object with an existing material and go to Rhino material properties page
- add the new object to the selection (select with shift button)
- press "edit" material and close the dialog again
- now, both object use the material of the first choosed object

Some times, this effect has unintentional mixed my materials, but now I use this trick sometimes.