WIL extender Dlls are special Dlls designed to extend the built-in function set of the WIL processor. These Dlls typically add functions not provided in the basic WIL set, such as network commands for particular networks (Novell, LAN Manager and others), MAPI  and other important Application Program Interface functions as may be defined by the various players in the computer industry from time to time. These Dlls may also include custom built function libraries either by the original authors, or by independent third party developers. (An Extender SDK is available). Custom extender Dlls may add nearly any sort of function to the WIL language, from the mundane network math or database extensions, to items that can control fancy peripherals, including laboratory or manufacturing equipment.

WIL extenders must be installed separately. Up to 32 extender Dlls may be added. The total number of added items may not exceed 750 functions and constants. The AddExtender function must be executed before attempting to use any functions in the extender library. The AddExtender function should be only executed once in each WIL script that requires it.