Actually, you don't. Just calculate whether it's an INSERT, UPDATE, or DELETE and mark a column with I, U, or D. Remember that when a trigger fires, it won't contain mixed events. It will be because of an INSERT, UPDATE, or DELETE and never a mixture.

If I recall correctly, here's one of the faster ways to determine what the triggering action was.

IF NOT EXISTS (SELECT TOP 1 1 FROM DELETED)

SELECT @TriggerAction = 'I'

ELSE IF NOT EXISTS (SELECT TOP 1 1 FROM INSERTED)

SELECT @TriggerAction = 'D'

ELSE SELECT @TriggerAction = 'U'

;