To change a material assignment, do one of the following:
3ds Max asks whether you want to assign the material to the object or to the entire selection.
To change a map assignment:
3ds Max opens a Copy (Instance) Map dialog so you can choose whether to swap the two maps, or make the updated map either a copy or an instance of the original.
To edit a material:
If the material is already in a sample slot, 3ds Max won’t let you drop it on the new sample slot.