Gents,

what expression can I use in Microsoft Access if i want to create a table like this Password Valid from valid to ( expiration date)

that is to say the section needs to expire the old records and create a new one or change the record contents

Your question is not clear, this can be done using a scripting language that will set expiry date for the old password like this

CREATE TABLE storepwd (
new_pwd VARCHAR(32) NOT NULL,
expire_date DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00'
);

The above code is for mysql, and it should work on MS Access.
Your script should now check the expiry date and ask the user to change the password.

Something like SELECT * FROM storepwd WHERE expire_date >= 'Your expire date'

Launch Ur Access, Create ur table in design mode. create 3 or more columns (e.g. Password, StartDate, ExpiryDate)-Control the rest from your application. Make Ur Access db password-guarded and at the same time make provision for smart programmers like U in case they want to change system date to remain valid,