sql server db trigger when certain field changes

Question

is there anyway to put a condition in a SQL server trigger to say fire when field "XYZ" changes ?

EDIT:

what is the correct SQL syntax to basically insert into a new field

Field XZY has changes from Value A to value B

Answer 1

the trigger will always fire but you can break it's execution by using UPDATE() and COLUMNS_UPDATED methods inside the trigger

Answer 2

you can have a conditional section anywhere within your trigger statement using

IF UPDATE (column_name)
BEGIN
    IF (SELECT column_name FROM INSERTED) = 'B'
    BEGIN
        /* do something */
    END
END