How can you only have the symmetry modifier only effect certain parts of an object in 3ds Max 2011?

What I am trying to do Is model a knight character and am using the symmetry modifier to make his general shape. I was wondering how to make something only happen on one side like a face protector that is not go on both sides of the axis or a curved line of the armor. If there is no easy answer to this how would I go about doing this? Thanks a million and God bless you.