How to import one excel file 20 times in an access table and the table should keep the old records.how to do that thanks

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

Howdy. Also, it would be more helpful if your title reflected what you are trying to do. "Help me" applies to every thread! and it is NOT very helpful. ;)