You can’t be this naive. Even a third grader knows congress can change the laws anytime. Only constitutional amendment would guarantee 2/3 requirement
You can put a provision in the Bill requiring a 2/3 vote. Once it is passed by both houses and signed by the President, it becomes law. The only way to change it would be to repeal the law which would require both houses and a Presidential signature. Short of that, they would have to follow the 2/3 vote requirement as it would be the LAW.
You can’t be so naive as to not know a Bill doesn’t become a Law until passed by BOTH HOUSES and signed by the President, or if Vetoed overridden by a 2/3 vote in both houses.