#1.  Worksheets are protected--not parts of worksheets.
    But in xl2002+, you have finer control over what you can do on a protected
    worksheet.

    But even if you protect that worksheet with that column hidden, it
    wouldn't take much to unprotect worksheet--excel's worksheet and workbook
    (under Tools|Protection) is not made for security purposes--it's usually
    used to stop simple typos (overwriting labels or formulas).

#2.  Is this a one time thing?

If yes, maybe some manual effort.

Insert a new column between B and C.  (so that old C is now new D.)

In C3, put this:

=if(isnumber(match(b3,d:d,0)),b3,"")
Drag down to C346.

Select column C and edit|copy, edit|paste special|values to get rid of the
formulas.

Now you have the words that match up in column C.

Now insert a new column E next to column D (which was old column C).

Put this in E3:
=if(isnumber(match(d3,b:b,0)),"",d3)
And drag down to E278.

Now the words that are missing from the first list are in column E.

Select column E and edit|copy, edit|paste special|values to get rid of the
formulas.

Now be careful.  Sort column E (not any other column!).

Copy those cells with words in them under the last entry in column C (C347???).

Delete column E (we're done with it).