(a) Every agreement, promise or undertaking is unenforceable unless it
or some note or memorandum thereof is in writing and subscribed by the
party to be charged therewith, or by his lawful agent, if such
agreement, promise or undertaking:
(1) Is a contract to establish a trust.
(2) Is a contract to make a testamentary provision of any kind.
(3) Is a promise by a personal representative to answer for the debt
or default of his decedent.
(b) A contract to make a joint will, or not to revoke a joint will, if
executed after the effective date of this paragraph can be established
only by an express statement in the will that the instrument is a joint
will and that the provisions thereof are intended to constitute a
contract between the parties.