Transaction Variants

I want to restrict changes to the fields in Goods movement forone group of users.

Can any one explain these steps in detail?

1. Create a transaction variant for CO11N

2. Create a new transction code for the transaction variant and assign an authorization object to it

3. Divide the users into this two transaction code. Those who can change the field using CO11N. For those that have limited

field change, give them the authorizationfor ZCO11 (this is a new transaction code you have to create).