Yes. Your will is valid and effective until it is revoked, destroyed or invalidated by writing a new will. You can make a whole new will or you may alter an existing will by making a codicil. A codicil modifies an existing will so long as it is executed in compliance with applicable state law. You cannot simply cross out language within your current will or add a new provision as this type of action does not usually meet the legal requirements for executing a valid will.