Well you should probably plan this out a bit...
How many rows are you expecting in the table?
What type of activity is expected? Ex. 10% Insert, 20% Update, 70% Select.
At what point do you want the record to be copied over... Insert, Update, Both?
When the trigger fires do you want to handle just the records modified or all the records that fit the criteria within the table?
Could this be handled with a nightly or hourly job instead?
Once you can answer these questions then we'll be able to come up with a good solution.