Hi,
Version of Word? What kind of locking?
"It refers to a field?" What is it? Can you give the exact message?
A field is a dynamic placeholder in a Word document. It shows information
that can automatically change when something else changes. For instance, you
can type in the date, or you can insert a DATE field. The typed date will
always remain what you typed, the DATE field will show the current date when
you open the document two weeks later. (Seldom what you want.)
http://addbalance.com/usersguide/fields.htm
In a document that needs to be unlocked, often fields are FormFields. Those
are places that the user can type in when the rest of the document is
protected. Such forms are called "online forms" by Word.