How to limit the available DateTime ranges in a Google form? Only Next 4 weeks may be available, and strictly between 17:30PM < 20:30PM date

Question

I would like to know: How to limit the available DateTime ranges in a Google form? Only Next 4 weeks may be available, and strictly between 17:30PM < 20:30PM date. Indeed, I am free to help a non-profit association 3 hours everyday, but I am now spending more time replying email for appointments. I know there is a lot of tools to do that, but i prefer Google products. I am very new in programming Kind regards