You're not a real detail kind of guy based on your post, I would say don't update at all. but if I am reading it incorrectly here is a place to start...
You will first need to add a column to your spreadsheet to differentiat a date/time of the updates. You will then need to make an update/append query to update a table that is setup like your spreadsheet.
This is only one way to go about it, but it is a place to start.
HTH