Setup ?

Hi, I am trying to create an access database that has historical data and new
data is imported in monthly. I need it to be able to check each time if it's
a new member before it dumps into the data. If it's new it needs to be
tagged new? And then I need to be be able to run comparisons on future data
to that first event? What's the best way to clone the records together?

1) Do I create a working table (holds everything)
2) Create a temp table (monthly table)
3) Somehow run something that checks and tags? How do I do this?
4) Then append?

--
Thank you in advance!!!!