Legal Question in Real Estate Law in California

You need to be more clear for me to understand what you are asking. If you are speaking about an offer to buy property, the person making the offer can agree to make a new offer with the same terms. if the offer has expired, technically it can not be extended. You can just send an e-mail saying you renew your offer of $xx good until a/s/dd.

I suggest reposting, with more information of what it is you are trying to do. It would help us give you the right answer.