If, on or after November 23, 1970, an association executes a modification agreement with a borrower respecting a mortgage contract, deed of trust, real estate sales contract, or modifies any note or negotiable instrument issued in connection therewith which was executed before November 23, 1970, and the modification agreement or modified note includes a variable interest rate, it shall comply with Civil Code Section 1916.5 or 1916.6 and with these regulations.