Script to mail user before the expiry date of user accounts

Hi Experts,

We have some user accounts (generic ID's) which are been created for a few months on users demand. I was trying to write a script which mail's to the mail id mentioned in E-mail Tab properties of account, about the expiry date, before 7 days. This may help the user to renew the generic accounts if required.

Could you please help me, how do I use the search-adaccounts or get-aduser like cmdlets in a algorithm.

Or please let me know if this can done with a simple script.

Thanks for help