Chapter 19. XLLs and the C API

This chapter in no way attempts to provide a complete guide to programming Excel using the C API. That would be a book-length topic in its own right. A skilled C++ programmer with an in-depth knowledge of the Excel C API can create add-ins that can do anything a VBA add-in can do.

Instead, this chapter focuses on the core strength of the C API and what is arguably the most common use for it in Excel development: programming custom worksheet functions. Even this topic is too large to be covered in a single chapter, so we get you started with solid fundamentals and then point you to additional resources at the end of the chapter.

All the examples discussed in this chapter assume that you are running Microsoft Visual ...

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