Is it possible to have a “future” settlement in case of divorce?
Yes. But your question tells me, all in caps, that you need to undergo a significant learning curve about legal matters before you sign or agree to anything. Otherwise you are shooting yourself in the foot. I'll get to that in a moment.
If there is such thing, do I get notarized then?
This and other requirements depend on the laws in your jurisdiction. For instance, see In re Marriage of Plaisted v. Plaisted, (Court of Appeals of Minnesota, 2008):
[T]o be a valid postnuptial agreement, an agreement must strictly
comply with the formalities enumerated by statute. Minn. Stat. §
519.11 (2006) (requiring that, prior to the agreement, full disclosure of earnings and property be made and each spouse be given an
opportunity to be advised by independent legal counsel; the agreement
itself must be a writing signed by both spouses before two witnesses
Now my main point ...
Contracts are premised on the covenant of good faith and fair dealing. Your description casts doubt on whether these elements still exist at this point in your marriage.
The spouse's demand for your assets "IF [you] cause the divorce to happen" is a time bomb for at least two reasons. First, it is predictable and very typical for spouses (& their lawyers) to blame each other in court, thereby attributing to each other the cause of divorce.
Second, the term "to cause the divorce to happen" is too ambiguous and ought to be defined very precisely in an agreement. For instance, "to cause" can mean the sole act of filing --or deciding to file-- divorce pleadings in court; it can mean a spouse's conduct that prompts the other spouse to pursue divorce; or it can mean anything in between.
Divorce proceedings are a source of tremendous wealth to lawyers, obviously at the expense of their clients. See this news report on how lawyers essentially team up, unbeknownst to their clients, to drag a case for as long as it takes them to deplete their clients' savings. Judges turn a blind eye on these dynamics, in part because allowing those lawyers to keep profiting will make it easier for the judge to systematically secure his reelections till he opts to retire. Under such circumstances, a postnuptial agreement is nothing but dead letter.
Besides developing some expertise in contract law as well as the drafting of contracts, you should get acquainted with case law (if in the US, see leagle.com) --especially of your jurisdiction-- and the applicable legislation. When studying court opinions, please be mindful that they might be unreliable regarding the facts of a case: judges can (and do) distort the record on appeal so they can force an improper outcome. The usefulness of these resources is that they enlighten on the interpretation & purported application of statutory law, as opposed to reading only the applicable legislation.