If you're importing weekly, you can add another column to your one Access
data table, something along the line of DateCreated. YOu can set that date
in your append queries the same as you set the "OriginalSource" text.

You'll need some mechanism for identifying the current data set for when you
want to select data. You could have a parameter table with a row containing
the current data set's DateCreated, or you can use grouping query to select
Max(DateCreated), although this is less reliable. If you store the date to
use for current data and refer to that, you don't get hit in the face is
someone is running a report (expecting what they think of as "current data")
while you are in the middle of creating what is about to become the next
current data.