Locking A field after it has the data entered and Locking opportunities once they are closed

Hello.

I have two questions in regards to locking things down.

1) After someone enters an opportunity name in the field, I need to have this then automatically lock/not be able to be changed by people.  I realize this is probably a horrible idea, but it is what "the powers that be" have insisted.

2) Also, when a deal is closed out as either a win or a loss, how to I then have those fields automatically lock so that no further changes/updates can be made.

Thanks a ton.

Glen