These must only be called after deliver is called. deliver-keyword must be one of the legal keywords to deliver (see Alphabetical list of deliver keywords, or can be displayed by calling deliver-keywords).
delivery-value returns the value associated with deliver-keyword. When deliver is called, the values associated with each keyword are initialized from the arguments to deliver or using their default values (which are printed by deliver-keywords), or set to
nil. Values can be changed later by user actions that were added to the "Delivery actions" action list, and then by the system. Before starting the shaking operations, the values of the keywords are reset, and
delivery-value cannot be called after the shaking.
(setf delivery-value) can be used to set the value of a keyword. Since the user actions are done before the system actions, these system actions (which also use
delivery-value to access the keyword's value) will see any change that the user actions effected.
LispWorks Delivery User Guide - 15 Feb 2015