I am wondering how you would set off a trigger based on only one column changing? Is this possible? I know you can set a trigger to run if there has been a delete, update or insert based on the table, but how would you narrow this down to one column having changed?

With triggers, I don't believe you can.

Closest you can do is the following....suppose you want to detect if ProductMaster.ListPrice has changed...

DECLARE @NumRowsChangedByUpdate int

SET @NumRowsChangedByUpdate = 
    (select  Count(ProductMaster.ProductKey) from ProductMaster
                                         JOIN Inserted on ProductMaster.ProductKey = Inserted.ProductKey
                                         join Deleted on ProductMaster.ProductKey = Deleted.ProductKey
                                                where Inserted.ListPrice <> Deleted.ListPrice)

if @NumRowsChangedByUpdate > 0
          -- then go do something

However, if you're using Change Data Capture, you could theoretically tap into something using CDC if you set it up for just a single column, though it's going to involve some work.

What specifically do you want to do when the single column value changes?