What password are you referring to? Did you create your own authentication scheme, or are you using Access built-in workgroups (ULS)?
If you created your own, you could simply add a "forgot/reset password" button to your login form. From there it is up to you how to handle it, you could simply reset the password to a default (not very secure as anyone could reset anyone elses password), or something like what website do where they record/ask you a security question before reseting, or email the user their new password. All these are possibilities but would require you to capture information you likely aren't capturing today.
If you are using workgroup security (*.mdw file) then the simple answer is you can't add a reset button. None of your code will execute until they login successfully, and if they forgot their password that can't happen.
ASAP
