U

 Section 2-209(2) of the Uniform Commercial Code provides that 'a signed agreement which excludes modification or rescission except by a signed writing cannot be otherwise modified or rescinded, but except as between merchants such a requirement on a form supplied by the merchant must be separately signed by the other party.' (As several other subsections of section 2-209 are relevant to the appeal, we have printed the entire section as an Appendix to this opinion.) The meaning of this provision and its proviso is not crystalline and there is little pertinent case law. One might think that an agreement to exclude modification except ...